feat(core): add agentsmd-audit skill files

The previous commit only landed the research-folder rename — a multi-path
git add silently failed and left CONTEXT.md, ADR-0012, and the actual skill
files unstaged. This lands them: the agentsmd-audit skill itself (three
deterministic validators for secrets, structure, and drift against a target
repo's AGENTS.md), its bats test suite, provenance record, and the
CONTEXT.md/ADR entries documenting why this lives in core rather than
kyberforge.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

plugins/core/skills/agentsmd-audit/SKILL.md

@@ -0,0 +1,68 @@
+---
+name: agentsmd-audit
+description: >
+  Use when the user wants to review a repo's AGENTS.md file, says "audit this
+  AGENTS.md", "check my AGENTS.md", "is this AGENTS.md any good", or wants to
+  know if AGENTS.md is safe to commit — even if they don't use the word
+  "audit". Also invoke proactively after agentsmd-author creates or updates
+  AGENTS.md, or after a hand-edit made outside agentsmd-author. Audits a
+  target repo's AGENTS.md file(s) — root and any nested monorepo files — for
+  embedded secrets/credentials, structural completeness against the
+  agents.md common-sections checklist, and drift (referenced commands or
+  paths that no longer resolve against the repo). Produces a compact
+  findings report (findings only, no PASS noise) with Why and Fix per
+  finding. Do not use to audit CLAUDE.md, .cursor/rules, or other
+  provider-specific adapter files — that's provider-adapter-author's
+  self-contained concern. Do not use to fix or write AGENTS.md content — use
+  agentsmd-author instead.
+allowed-tools: Bash Read
+metadata:
+  category: docs
+  source_keys:
+    - agents-md-official
+    - context7-websites-agents-md
+    - context7-agentsmd-agents-md
+    - governance-secrets-hard-prohibition
+  version: "0.1.0"
+---
+
+## Gotchas
+
+- Always run all three checks — this skill does a single combined pass, not staged/gated passes. Don't skip structure or drift checks just because a secrets FAIL was found.
+- Never inspect or mention provider-specific adapter files (`CLAUDE.md`, `.cursor/rules/*.mdc`, `copilot-instructions.md`, etc.) — that's out of scope. If one exists and duplicates AGENTS.md content, that's `provider-adapter-author`'s concern, not this skill's.
+- A missing common section (e.g. no "Security" heading) is informational, not a failure — not every repo needs every section from the checklist. Only flag a FAIL when the file is empty, entirely unfilled placeholder text, or contains a real embedded secret/stale reference.
+- Gather findings internally; don't narrate PASS/FAIL per check as you go — surface them only in the final report.
+
+## Step 1 — Run the validators
+
+```bash
+bash scripts/validate-secrets.sh <repo-root>
+bash scripts/validate-structure.sh <repo-root>
+bash scripts/validate-drift.sh <repo-root>
+```
+
+Each script walks the repo for every `AGENTS.md` file (root and nested, excluding `.git`, `node_modules`, `vendor`, and similar) and prints `FAIL`/`INFO`/`SUGGESTION` lines with `Why`/`Fix` (or `Note`) per finding. A nonzero exit means at least one FAIL was found in that dimension. If a script cannot execute (`python3` unavailable, Bash denied), fall back to manual review: scan for real-looking credentials, check common sections are present, and spot-check a few referenced commands/paths by hand.
+
+## Step 2 — Report
+
+Open with a coverage line:
+
+```text
+Checked: secrets · structure · drift
+```
+
+Then output only findings that were found, in this order within a repo: `### Secrets`, `### Structure`, `### Drift`. Omit a dimension heading entirely if it produced nothing — its absence confirms it passed. Report each finding verbatim as emitted by the scripts (they already carry file:line, Why/Fix or Note).
+
+Close with a result block:
+
+```text
+## Result
+
+PASS
+PASS · P info
+PASS (N suggestions) · P info
+FAIL (N fails)
+FAIL (N fails) · P info
+```
+
+INFO and SUGGESTION findings are observational — they never flip PASS to FAIL. Do not fix anything — this skill reports and proposes only. Point the user to `agentsmd-author` to apply fixes.