feat(ci): gate the vendored pi-extensions skill floor, and bake python3-yaml

Follows ecfd2fc, which refreshed the stale floor by hand. A one-off refresh
fixes the symptom; this makes the drift impossible to reintroduce silently.

scripts/check-skill-floor.sh compares the repo floor
(rootfs/usr/local/share/pi-devbox/skills/pi-extensions/) against the package
repo it is a snapshot of, wired in as a new `skill-floor` job in lint.yml.

DIRECTORY hash, not `sha256sum SKILL.md`, using the same tree_sha256 pipeline
Dockerfile.variant uses for skillset_snapshot_tree_sha256 and for the reason
already documented there: a file-only compare answers "did this one file
change", not "is this the same skill". Verified by NEGATIVE CONTROL rather
than asserted -- with SKILL.md left byte-identical and only
evaluate-extension-usage.py edited, the directory check fails (rc=1) where a
file-only compare would have passed. Seven behaviour tests, each with its
expected rc written down before running: in-sync via local dir (0), in-sync
via anonymous remote clone (0), missing --package-dir (2), bad argument (2),
content drift (1), the sibling-file case (1), and --warn-only over drift (0).

Exit codes 0 in sync / 1 drift / 2 cannot-run, matching scripts/lint-shell.sh:
a gate that cannot run must not pass, so an unreachable package repo is a red
2 and never a green tick. A ref with no skill/ is NOT drift -- that is the
documented fallback -- but it emits ::warning:: because it is precisely the
condition under which the floor ships.

Gating on another repo is normally a smell. It is proportionate here because
the check can only fire when skill/ itself changed, which is exactly when the
floor has gone stale; pi-extensions commits that leave skill/ alone cannot
turn this red. It also needs no secret: pi-extensions is anonymously clonable
(verified with `git ls-remote` and no credentials), so it cannot start failing
when a token expires.

Also bakes python3-yaml (552 KB, zero extra deps) into Dockerfile.base. This
is the shellcheck story repeating exactly: scripts/check-workflow-shell.sh --
the guard against the Gitea sh/dash footgun that broke resolve-versions
(ed49b8d) and promote-base-latest (b7197e8) -- hard-exits with "python3 yaml
module missing", so a gate this repo already owns could not be run locally by
anyone. lint.yml installing it explicitly in CI was the evidence. Found while
wiring the job above: the guard could not be run before pushing.

CHANGELOG Unreleased updated for both this and ecfd2fc, including an explicit
note on what is NOT fixed -- the silent-fallback half still has no manifest
flag recording which copy was served.

Verified locally with every gate this repo owns, all green: lint-shell.sh (15
files clean), check-workflow-shell.sh, check-base-hash.sh, actionlint 1.7.7
(pinned, same version as CI), hadolint 2.14.0, and the new check itself.

.gitea/workflows/lint.yml

@@ -137,3 +137,38 @@ jobs:
 
       - name: Run hadolint
         run: hadolint Dockerfile.base Dockerfile.variant
+
+  skill-floor:
+    # Gate the VENDORED pi-extensions skill snapshot in rootfs/ against the
+    # package repo it is a snapshot of. Its own job rather than a step in
+    # `actionlint`, so "the floor is stale" is a distinct red name in the runs
+    # list instead of being buried in a lint job that is about something else.
+    #
+    # The gap it closes, measured 2026-09-10: the floor sat at 34284 B, untouched
+    # since fa04d20 (2026-07-30), while the package copy was 38973 B.
+    # Dockerfile.variant copies the fresh package copy over the SERVED path but
+    # never writes back to the floor, so nothing in the repo ever noticed. That
+    # matters because the floor is a FALLBACK: the copy is guarded by
+    # `if [ -f /opt/pi-extensions/skill/SKILL.md ]`, so a build whose clone
+    # yields no skill/ ships the vendored snapshot and still goes green, with no
+    # manifest flag or label saying which copy was served.
+    #
+    # Gating on another repo is normally a smell; it is proportionate here
+    # because the check compares the skill DIRECTORY hash, so it can only fire
+    # when that directory actually changed — which is exactly when the floor has
+    # gone stale. pi-extensions commits that leave skill/ alone cannot turn this
+    # red. No secret is needed either: the repo is anonymously clonable (verified
+    # 2026-09-10 with `git ls-remote` and no credentials), so this cannot start
+    # failing when a token expires.
+    #
+    # Exit codes are 0 in sync / 1 drift / 2 cannot-run, matching
+    # scripts/lint-shell.sh: a gate that cannot run must not pass, so an
+    # unreachable package repo is a red 2 rather than a green tick.
+    runs-on: ubuntu-latest
+    container:
+      image: catthehacker/ubuntu:act-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Vendored pi-extensions skill floor matches the package
+        run: bash scripts/check-skill-floor.sh

CHANGELOG.md

@@ -92,6 +92,66 @@ derivation's `mine` query at the newest end (`order: "desc"`); with the previous
 default `asc` + `limit: 100`, a device passing 100 authored events would have its
 recent replies fall out of the join window and see answered asks resurface.
 
+**Four small packages, each chosen from a gap that was measured rather than
+imagined.** All four were picked by looking back at a real session — the
+`gitea.egl.lan`/FreeIPA debugging of 2026-09-09..10 — and asking which absences
+actually cost time, not which tools sound useful. `bind9-dnsutils` (~6.1 MB, 10
+packages): `dig`, `host` **and** `nslookup` were all absent, so the container
+could resolve names but had no way to interrogate a *specific* nameserver —
+`getent hosts` only follows the resolver's default path, so diagnosing "gateway
+`172.16.88.1` NXDOMAINs the `egl.lan` zone while `10.20.253.1` is authoritative
+for it" had to be hand-rolled in `python3`. Note the package name: plain
+`dnsutils` is transitional in trixie. `ldap-utils` (1244 KB, **zero** extra deps):
+the fleet authenticates against FreeIPA, yet every LDAP probe had to be run by
+SSHing to an already-enrolled host; this gives simple binds only, since GSSAPI
+would additionally need `krb5-user` + `libsasl2-modules-gssapi-mit`, which is a
+Kerberos-client decision rather than a tool. `xxd` (198 KB) is frank convenience
+— `od -c` already does the job. `python3-yaml` (552 KB, zero extra deps) is the
+shellcheck story repeating exactly: `scripts/check-workflow-shell.sh`, the guard
+against the Gitea `sh`/dash footgun that broke `resolve-versions` (`ed49b8d`) and
+`promote-base-latest` (`b7197e8`), hard-exits with "python3 yaml module missing"
+without it — and `lint.yml` installing it explicitly in CI was the evidence the
+image lacked it. **`netcat-openbsd` was proposed and deliberately rejected**:
+measured redundant, because `socat` is already baked and bash's `/dev/tcp` does
+reachability checks with zero packages. The reason is recorded in
+`Dockerfile.base` so the omission reads as a decision rather than an oversight.
+
+**The vendored `pi-extensions` skill floor was 41 days stale, and is now gated so
+it cannot silently rot again.** `rootfs/usr/local/share/pi-devbox/skills/pi-extensions/`
+sat at 34284 B, untouched since `fa04d20` (2026-07-30), while the package copy
+was 38973 B — four copies of one skill existed across the fleet with three
+different sizes. `Dockerfile.variant` copies the freshly-cloned package copy over
+the **served** path but never writes back to the repo floor, so nothing in the
+repo ever noticed. That is worse than ordinary staleness because the floor is a
+**fallback**: the copy is guarded by `if [ -f /opt/pi-extensions/skill/SKILL.md ]`,
+so a build whose clone yields no `skill/` keeps the vendored snapshot and still
+goes **green**, with no manifest flag and no label recording which copy was
+served — the image would ship a July skill and nothing would say so. The floor is
+refreshed here from `pi-extensions@c64c122`, and the new `skill-floor` job in
+`lint.yml` runs `scripts/check-skill-floor.sh` to keep it that way.
+
+The check compares the **directory** hash, using the same `tree_sha256` pipeline
+`Dockerfile.variant` uses for `skillset_snapshot_tree_sha256` and for the same
+documented reason: a `sha256sum SKILL.md` answers "did this one file change", not
+"is this the same skill", and `pi-extensions` ships two files. That is not
+hypothetical — it was **verified by negative control**: with `SKILL.md` left
+byte-identical and only `evaluate-extension-usage.py` edited, the directory check
+correctly fails while a file-only compare would have passed. Exit codes are `0`
+in sync / `1` drift / `2` cannot-run, matching `scripts/lint-shell.sh`, so an
+unreachable package repo is a red `2` rather than a green tick. Gating on another
+repo is normally a smell; it is proportionate here because the check can only
+fire when `skill/` itself changed — which is exactly when the floor has gone
+stale — and it needs no secret, since `pi-extensions` is anonymously clonable
+(verified with `git ls-remote` and no credentials).
+
+> **What this does *not* fix, stated so nobody reads more into it than is there.**
+> The floor is now fresh and guarded, but the *silent-fallback* half remains:
+> if the build-time copy is ever absent, the build still succeeds with no
+> manifest flag or OCI label recording that the vendored snapshot was served
+> instead of the package copy. The durable fix for that is a manifest field
+> alongside the existing `skillset_snapshot_tree_sha256`, which this change does
+> not add.
+
 ---
 
 ## v1.8.14 — 2026-09-08

Dockerfile.base

@@ -162,6 +162,19 @@ ENV DEBIAN_FRONTEND=noninteractive
 #                  /dev/tcp does reachability checks with zero packages
 #                  (verified against gitea.egl.lan:3000). Recorded here so the
 #                  omission reads as a decision rather than an oversight.
+#   python3-yaml — PyYAML. Added 2026-09-10 for precisely the same reason as
+#                  shellcheck above: a gate this repo ALREADY OWNS could not be
+#                  run locally by anyone. scripts/check-workflow-shell.sh — the
+#                  guard that catches the "bash-only syntax under Gitea's default
+#                  sh/dash shell" footgun that broke resolve-versions (ed49b8d)
+#                  and promote-base-latest (b7197e8) — hard-exits with "ERROR:
+#                  python3 yaml module missing" without it. lint.yml installs it
+#                  explicitly in CI (`shellcheck python3-yaml`), which is itself
+#                  the evidence that the image lacked it. Measured 2026-09-10
+#                  while wiring the skill-floor job: the guard could not be run
+#                  before pushing — the same write → push → wait-for-CI loop that
+#                  shellcheck was baked to shorten. 552 KB, and pulls ZERO extra
+#                  packages under --no-install-recommends.
 RUN apt-get update && \
     apt-get upgrade -y --no-install-recommends && \
     apt-get install -y --no-install-recommends \
@@ -206,6 +219,7 @@ RUN apt-get update && \
     bind9-dnsutils \
     ldap-utils \
     xxd \
+    python3-yaml \
     && ln -s /usr/bin/fdfind /usr/local/bin/fd \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/*

scripts/check-skill-floor.sh

@@ -0,0 +1,166 @@
+#!/usr/bin/env bash
+# check-skill-floor.sh — fail when the vendored pi-extensions skill snapshot in
+# rootfs/ ("the floor") has drifted from the package repo it is a snapshot of.
+#
+# THE DEFECT THIS EXISTS TO CATCH, measured 2026-09-10.
+# rootfs/usr/local/share/pi-devbox/skills/pi-extensions/ ships a vendored copy
+# of the pi-extensions skill so the skill is ALWAYS present in the image.
+# Dockerfile.variant then copies the freshly-cloned package copy OVER the served
+# path at /usr/local/share/... — but it never writes back to the repo floor. So
+# the floor only silently rots, and it had: 34284 B, untouched since fa04d20
+# (2026-07-30), while the package copy was 38973 B. Four copies existed with
+# three different sizes.
+#
+# Why that is worse than ordinary staleness: the floor is a FALLBACK. The copy
+# step is guarded by `if [ -f /opt/pi-extensions/skill/SKILL.md ]`, so a build
+# where the package clone yields no skill/ keeps the vendored snapshot and still
+# succeeds — green, with no manifest flag and no label saying which copy was
+# served. The image would ship a July skill and nothing would say so. Keeping
+# the floor fresh means that fallback is harmless instead of a silent regression.
+#
+# WHY A DIRECTORY HASH AND NOT `sha256sum SKILL.md`.
+# The same pipeline Dockerfile.variant uses for skillset_snapshot_tree_sha256,
+# and for the same documented reason: a file-only compare answers "did this one
+# file change", not "is this the same skill". pi-extensions ships TWO files
+# (SKILL.md + evaluate-extension-usage.py), so a sibling-file edit would pass a
+# file-only check. If you change the pipeline here, change it there too.
+#
+# WHY GATING ON ANOTHER REPO IS PROPORTIONATE HERE, since that is normally a
+# smell: this fires only when the package's skill/ DIRECTORY HASH changes, which
+# is exactly and only when the floor has genuinely gone stale. pi-extensions
+# commits that do not touch skill/ leave the hash alone and cannot turn this red.
+# The repo is also anonymously clonable (verified 2026-09-10 with `git ls-remote`
+# and no credentials), so this needs no secret and cannot break on token expiry.
+#
+# Exit codes — deliberately three, matching scripts/lint-shell.sh's philosophy
+# that a gate which cannot run must not pass:
+#   0  in sync (or the package legitimately has no skill/ at this ref)
+#   1  DRIFT — the floor differs from the package
+#   2  cannot run — no package copy could be obtained
+set -euo pipefail
+
+REPO_ROOT=$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)
+FLOOR_DIR="${REPO_ROOT}/rootfs/usr/local/share/pi-devbox/skills/pi-extensions"
+
+# Defaults mirror Dockerfile.variant's ARGs so this checks what the build builds.
+PI_EXTENSIONS_REPO="${PI_EXTENSIONS_REPO:-https://gitea.jordbo.se/joakimp/pi-extensions.git}"
+PI_EXTENSIONS_REF="${PI_EXTENSIONS_REF:-main}"
+
+PACKAGE_DIR=""
+WARN_ONLY=0
+TMPDIR_CLONE=""
+
+usage() {
+  cat <<'EOF'
+Usage: scripts/check-skill-floor.sh [options]
+
+  --package-dir DIR   Compare against an existing skill directory instead of
+                      cloning. In a devbox container use /opt/pi-extensions/skill
+                      for a fully offline run.
+  --warn-only         Report drift but exit 0 (advisory use, e.g. a local hook).
+  -h, --help          This text.
+
+Environment: PI_EXTENSIONS_REPO, PI_EXTENSIONS_REF (default main) — both mirror
+the Dockerfile.variant ARGs of the same name.
+EOF
+}
+
+while [ $# -gt 0 ]; do
+  case "$1" in
+    --package-dir) PACKAGE_DIR="${2:-}"; shift 2 ;;
+    --warn-only)   WARN_ONLY=1; shift ;;
+    -h|--help)     usage; exit 0 ;;
+    *) echo "::error::unknown argument: $1" >&2; usage >&2; exit 2 ;;
+  esac
+done
+
+cleanup() {
+  if [ -n "$TMPDIR_CLONE" ]; then rm -rf "$TMPDIR_CLONE"; fi
+}
+trap cleanup EXIT
+
+# Identical to Dockerfile.variant's tree_sha256(): relative paths + per-file
+# sha256 over a sorted `find`, folded into one digest. Deterministic, never
+# readdir order.
+tree_sha256() {
+  ( cd "$1" && find . -type f -print | LC_ALL=C sort | xargs -r sha256sum ) \
+    2>/dev/null | sha256sum | cut -d' ' -f1
+}
+
+if [ ! -d "$FLOOR_DIR" ]; then
+  echo "::error::floor directory is missing: ${FLOOR_DIR}"
+  echo "::error::rootfs/ is supposed to guarantee the skill is always in the image."
+  exit 2
+fi
+
+SOURCE_DESC=""
+if [ -n "$PACKAGE_DIR" ]; then
+  if [ ! -d "$PACKAGE_DIR" ]; then
+    echo "::error::--package-dir does not exist: ${PACKAGE_DIR}"
+    exit 2
+  fi
+  SOURCE_DESC="local directory ${PACKAGE_DIR}"
+else
+  command -v git >/dev/null 2>&1 || { echo "::error::git not found; cannot obtain the package copy."; exit 2; }
+  TMPDIR_CLONE=$(mktemp -d)
+  # Fetch the single ref shallowly. `git fetch <ref>` accepts a branch, a tag
+  # and (on Gitea) a reachable commit, which is why this is not `clone --branch`
+  # — CI resolves PI_EXTENSIONS_REF to a 40-hex SHA before the build.
+  if ! ( cd "$TMPDIR_CLONE" \
+          && git init -q . \
+          && git remote add origin "$PI_EXTENSIONS_REPO" \
+          && git fetch -q --depth 1 origin "$PI_EXTENSIONS_REF" \
+          && git checkout -q FETCH_HEAD ) 2>/dev/null; then
+    echo "::error::could not fetch ${PI_EXTENSIONS_REF} from ${PI_EXTENSIONS_REPO}"
+    echo "::error::Cannot determine whether the floor is stale, so this is exit 2, not a pass."
+    echo "::error::For an offline run, pass --package-dir /opt/pi-extensions/skill"
+    exit 2
+  fi
+  PACKAGE_SHA=$( cd "$TMPDIR_CLONE" && git rev-parse --short HEAD )
+  PACKAGE_DIR="${TMPDIR_CLONE}/skill"
+  SOURCE_DESC="${PI_EXTENSIONS_REPO} @ ${PI_EXTENSIONS_REF} (${PACKAGE_SHA})"
+fi
+
+# A ref with no skill/ is the documented fallback case: Dockerfile.variant keeps
+# the vendored snapshot and the build succeeds. Nothing to compare, so this is
+# not drift — but it IS the exact condition under which the floor ships, so say
+# so loudly rather than printing a silent green tick.
+if [ ! -d "$PACKAGE_DIR" ]; then
+  echo "::warning::package has no skill/ at this ref — the vendored floor is what will ship."
+  echo "  source : ${SOURCE_DESC}"
+  echo "  floor  : $(tree_sha256 "$FLOOR_DIR")"
+  exit 0
+fi
+
+FLOOR_HASH=$(tree_sha256 "$FLOOR_DIR")
+PKG_HASH=$(tree_sha256 "$PACKAGE_DIR")
+
+if [ "$FLOOR_HASH" = "$PKG_HASH" ]; then
+  echo "OK: vendored pi-extensions floor matches the package."
+  echo "  source     : ${SOURCE_DESC}"
+  echo "  tree_sha256: ${FLOOR_HASH}"
+  exit 0
+fi
+
+# `set -e` interacts badly with `[ … ] && x` as a bare statement, so both of
+# these are explicit if-blocks rather than AND-lists.
+LEVEL="error"
+if [ "$WARN_ONLY" -eq 1 ]; then LEVEL="warning"; fi
+
+echo "::${LEVEL}::vendored pi-extensions skill floor has DRIFTED from the package."
+echo "  source            : ${SOURCE_DESC}"
+echo "  floor tree_sha256 : ${FLOOR_HASH}"
+echo "  pkg   tree_sha256 : ${PKG_HASH}"
+echo ""
+echo "  per-file differences:"
+diff -rq "$FLOOR_DIR" "$PACKAGE_DIR" 2>&1 | sed 's/^/    /' || true
+echo ""
+echo "  Remedy — re-sync the floor and commit it:"
+echo "    cp -a <pi-extensions>/skill/. ${FLOOR_DIR}/"
+echo "    git add ${FLOOR_DIR#"${REPO_ROOT}/"} && git commit"
+echo ""
+echo "  NOTE this forces one full base rebuild: base_tag hashes Dockerfile.base"
+echo "  + rootfs/, and that rebuild is what re-bakes the refreshed floor."
+
+if [ "$WARN_ONLY" -eq 1 ]; then exit 0; fi
+exit 1