skills: trim two descriptions to a routing sentence, and assert their pointers

Every skill's name and description sit in the system prompt of EVERY request --
that block is the routing index -- while bodies are fetched on demand through
the read tool. Measured on this device: 24 discoverable skills cost 10,609
description chars (~2,652 tokens) per request, against 474,656 chars of bodies
(~119k tokens) that cost nothing until used. Bodies are 45x the descriptions,
which is what the spec's 1024-char description limit is protecting.

credential-incident-response (1022, two characters under the limit) and
pi-devbox-environment (923) were each carrying a table of contents of what
their body covers. Trimmed to what a description is actually for -- answering
"should I load this?" -- reclaiming 1,087 chars (~271 tokens) of permanent
context. 4,154 -> 3,067 across the five baked skills.

WHY ONLY THESE TWO. Both are named BY PATH from the always-loaded managed
block, so neither depends on description-matching to be found. pi-extensions is
left alone deliberately: check-skill-floor.sh compares the vendored copy to the
package repo by DIRECTORY HASH, so trimming ours alone registers as drift and
turns that gate red; and it is the one skill that also ships in the skillset
repo, where it runs on hosts with no pi-devbox managed block and genuinely needs
its description. pi-devbox-firstboot stays fuller than needed because it is the
skill a device with nothing else has to find.

NOTHING WAS DELETED, ONLY RELOCATED -- and that was checked rather than assumed:
all 18 enumerated items were confirmed present in the bodies BEFORE cutting
(frontmatter stripped, so the description's own line could not score its own
claim), and `git diff --stat` confirms both bodies are byte-identical.

THE TRIM CREATES A DEPENDENCY, SO IT IS NOW ASSERTED. smoke-test.sh checks both
pointers by path, next to the firstboot one. The premise of the cut is "the
block names them", which holds only while those lines exist -- reword the block,
drop a pointer, and the skill silently stops being reachable for a device that
did not already know it was there. Verified discriminating: a reworded block
fails the grep.

An instrument failure caught on the way, and the reason the coverage check was
re-run: my first pass used `grep -E 'a\|b'`, where \| is a LITERAL pipe in ERE,
so 8 of 18 items read as 0 hits. Every zero was a pattern containing \| and
every non-zero lacked one -- that correlation, not the content, was the finding.
With real alternation all 18 are present.

Loader re-verified on both trimmed skills: rc=0, no skill diagnostics.

rootfs/usr/local/share/pi-devbox/skills/credential-incident-response/SKILL.md

@@ -6,13 +6,7 @@ description: >-
   agent-authored note. Load this whenever a task involves a leaked/exposed
   secret, a token rotation, a "is this credential still live?" question, deciding
   whether to delete or scrub stored content, proving a corpus is clean, or
-  choosing scopes for a new API token. Covers the mandatory order of operations
-  (probe the issuer FIRST — severity before cleanliness), leak-free identity via
-  sha256[:8] fingerprints and when publishing one is safe,
-  why revocation beats deletion for anything already replicated, scopes derived
-  from measured consumers, the three places a secret hides in a Chroma palace, how to prove ABSENCE rather than assume it (instrument strength,
-  census vs class passes, the tokenisation trap where quoting decides detectability, why git filters never run on symlinks, self-tests that abort),
-  where this fleet's secrets live, and what rotation does NOT fix.
+  choosing scopes for a new API token.
 ---
 
 # Credential incident response

rootfs/usr/local/share/pi-devbox/skills/pi-devbox-environment/SKILL.md

@@ -6,14 +6,7 @@ description: >-
   shell prompt is prefixed `[devbox]`, or `~/.ssh-local/config` is present) and
   the task touches any of: reaching the Docker host or its LAN, SSH, DNS name
   resolution, what survives container recreate (persistence vs ephemerality),
-  running Python or other REPLs, tmux, or the pi-studio browser UI. Covers the
-  persistence model, the interactive-vs-tool-shell alias gotcha
-  (dssh/dscp/cat=bat exist only in interactive bash), host + LAN SSH
-  reachability and ControlMaster, split-horizon DNS mechanisms, the tmux
-  0-index constraint, uv-first Python, and pi-studio reachability. This skill
-  teaches MECHANISMS only — concrete hostnames, usernames, internal domains,
-  nameservers, and even the host OS vary per deployment and MUST be discovered
-  at runtime, never assumed or hardcoded.
+  running Python or other REPLs, tmux, or the pi-studio browser UI.
 ---
 
 # pi-devbox environment