fix(lint): tighten the SKILL.md word ceiling to 2770

MAX_WORDS=2900 was calibrated to the corpus median density and carried no
margin: at the densest observed 7.22 chars/word (~1.81 tokens/word) it permits
~5,240 tokens against the 5,000 it proxies for. 2770 holds the worst observed
density under the ceiling. The largest SKILL.md is 2,489 words, so the change
costs nothing today — 281 words of margin — and the header comment now argues
the new calibration rather than swapping the digits.

Both enforcement points move together, and a new test asserts they agree, since
a SKILL.md passing its own audit while the commit hook blocks it is the
disagreement this pair exists to prevent.

CONTEXT.md is deliberately left ungated: it is 2,816 words, and gating it would
block the build. Recorded here so the omission reads as a decision rather than
an oversight.

skill-audit's manual-fallback path listed only the line ceiling, so an agent
taking that path passed an oversized SKILL.md the hook then rejected. The word
ceiling is now named alongside it. agent-audit is deliberately unchanged: the
size hook scopes to SKILL.md only and agent-audit's validate.sh has no word
gate, so claiming it there would be false.

The Vale research doc still showed the MDX {/* vale off */} form under a
Markdown heading, contradicting CONTEXT.md and vale-run's troubleshooting
reference — that form suppresses nothing in plain .md. Fixed in both places it
appeared.

tests/run-tests.sh used mapfile (bash 4.0+) with unguarded array expansion,
though AGENTS.md tells contributors to run it and macOS ships bash 3.2. It now
collects via a while-read loop over process substitution and guards every
expansion. The newline-delimited find|sort pipeline is kept rather than -print0
with sort -z, whose BSD portability is the weaker link, and which matches
mapfile -t's previous behaviour exactly.

Refs: #85
ADR: 0013

plugins/kyberforge/skills/skill-audit/SKILL.md

@@ -37,7 +37,7 @@ bash scripts/validate-provenance.sh <skill-dir>
 scripts/vale-wrap.sh <skill-dir>/SKILL.md
 ```
 
-Note any structural FAILs — they will appear in the report as a `### Structure` dimension. If the script cannot execute (python3 unavailable, Bash denied, or permission error), perform structural checks manually: name format, name matches directory, description length ≤1024 chars, SKILL.md ≤500 lines, no unfilled `FILL IN:` placeholders, scripts executable and free of interactive prompts.
+Note any structural FAILs — they will appear in the report as a `### Structure` dimension. If the script cannot execute (python3 unavailable, Bash denied, or permission error), perform structural checks manually: name format, name matches directory, description length ≤1024 chars, SKILL.md ≤500 lines and ≤2770 words (the word count is a proxy for the ~5,000-token ceiling, and blocks a commit exactly like the line count does), no unfilled `FILL IN:` placeholders, scripts executable and free of interactive prompts.
 
 Note any Provenance FAILs and INFO findings from `validate-provenance.sh` — they surface in the report as a `### Provenance` dimension (separate from `### Structure`). The script embeds full FAIL/INFO format with Why and Fix per finding; surface them verbatim.
 

plugins/kyberforge/skills/skill-audit/scripts/validate.sh

@@ -140,7 +140,11 @@ else:
 # no single source to share. Keep the two in sync by hand: if they drift, this
 # audit will report a skill ready to ship that the commit hook then rejects.
 MAX_LINES = 500
-MAX_WORDS = 2900  # word-count proxy for the ~5,000-token ceiling
+# Word-count proxy for the ~5,000-token ceiling, calibrated to the densest
+# prose in the corpus (7.22 chars/word): 2770 words is ~20,000 characters,
+# ~5,000 tokens at 4 characters per token. See skill-size-check.sh's header
+# for the full measurement.
+MAX_WORDS = 2770
 
 line_count = len(content.splitlines())
 if line_count <= MAX_LINES: