chore(deps): node 22->24, actionlint 1.7.12, hadolint 2.15.1, skillset ref

Audited every component the image obtains OUTSIDE debian/apt. Of ~23, the 19
that resolve `latest` at build time were already current or refresh themselves
on the next rebuild, and the hard pins for pi (0.85.1), mempalace (3.9.0) and
pi-atelier (v0.10.1) were already newest. Four needed a human.

NODE_VERSION 22 -> 24 (LTS "Krypton"). This was a latent defect rather than
housekeeping: agent-browser publishes engines.node ">=24.0.0", so the image sat
BELOW a declared requirement -- v1.8.14 shipped node 22.23.2 with agent-browser
0.37.1, so every build installed it with an npm EBADENGINE warning and ran the
baked browser automation outside its supported range. pi (">=22.19.0") and
playwright (">=20") are satisfied either way. Verified before bumping, since a
missing NodeSource suite breaks every arch at once: setup_24.x returns HTTP 200
and node_24.x advertises `Architectures: amd64 arm64 armhf x86_64`, covering
the arm64 fleet and the amd64 CI runners. Nothing else pinned the node major.

actionlint 1.7.7 -> 1.7.12 and hadolint 2.14.0 -> 2.15.1, each RUN AGAINST THIS
TREE at the new version before being pinned -- both clean, no new findings. A
linter bump is the one dependency update that can turn CI red on unchanged
code, so it is verified locally rather than discovered on a round trip.

SKILLSET_SNAPSHOT_REF e9e09d9 -> 4d7c0ea via scripts/vendor-mempalace-skill.sh,
never by hand: that script is the only thing permitted to write the ARG,
because a cp without a matching bump yields a manifest that confidently lies.
This proved PROVENANCE-ONLY -- the ref was 6 commits behind, but
skills/mempalace/SKILL.md is byte-identical at both (3675bfab), so the snapshot
was already correct and only its recorded origin was stale. No rootfs/ bytes
changed, the smoke-test phrase canary stays valid, and this ARG alone would not
force a base rebuild (the node bump does).

Two measurement traps worth recording, since both would have produced a wrong
answer: GitHub's releases/latest reports pi-atelier v0.10.0 as newest because
v0.10.1 is a TAG WITH NO RELEASE OBJECT -- the pin was already current, and
`git ls-remote --tags` is the instrument that shows it. And gitea-mcp is hosted
on gitea.com, not GitHub, so querying api.github.com returned nothing at all
rather than an error.

Verified with every gate this repo owns, all green, using the NEW linter pins:
lint-shell.sh (15 files), check-workflow-shell.sh, check-base-hash.sh,
actionlint 1.7.12, hadolint 2.15.1, check-skill-floor.sh, and
vendor-mempalace-skill.sh --check.

.gitea/workflows/lint.yml

@@ -92,7 +92,7 @@ jobs:
 
       - name: Install actionlint (pinned)
         env:
-          ACTIONLINT_VERSION: 1.7.7
+          ACTIONLINT_VERSION: 1.7.12
         run: |
           curl -fsSL \
             "https://github.com/rhysd/actionlint/releases/download/v${ACTIONLINT_VERSION}/actionlint_${ACTIONLINT_VERSION}_linux_amd64.tar.gz" \
@@ -127,7 +127,7 @@ jobs:
 
       - name: Install hadolint (pinned)
         env:
-          HADOLINT_VERSION: 2.14.0
+          HADOLINT_VERSION: 2.15.1
         run: |
           curl -fsSL \
             "https://github.com/hadolint/hadolint/releases/download/v${HADOLINT_VERSION}/hadolint-Linux-x86_64" \