feat: /document-release skill — post-ship doc updates (v0.4.3) (#109)

* docs: update project documentation for v0.4.2

- README: skill count 9→10, added /document-release to skills table,
  install/uninstall sections, and dedicated section with example
- CHANGELOG: added /document-release bullet to v0.4.2 entry

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat: add /document-release skill with smart VERSION handling

New skill runs after /ship but before PR merge. Reads every doc file,
cross-references the diff, auto-updates factual changes, asks about
risky edits. CHANGELOG clobber protection: never uses Write tool on
CHANGELOG.md, only Edit with exact old_string matches.

Smart VERSION logic: instead of silently skipping already-bumped
versions, compares CHANGELOG entry scope against full diff and asks
if significant uncovered changes exist.

Also fixes gstack-upgrade/SKILL.md missing from skill-check.ts
SKILL_FILES array (existing inconsistency with gen-skill-docs.ts).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat: /review Step 5.6 — documentation staleness check

Review skill now cross-references code changes against doc files.
If a doc describes a feature that changed but the doc wasn't updated,
flags it as INFORMATIONAL with a pointer to /document-release.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* test: /document-release E2E with CHANGELOG clobber guard

E2E test creates a repo with existing CHANGELOG entries, runs
/document-release, and asserts original entries survive. Critical
guardrail against the incident where an agent replaced CHANGELOG
entries during conflict resolution.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* chore: bump to v0.4.3 — /document-release skill

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* chore: regenerate SKILL.md files after merge

* chore: regenerate SKILL.md files after merge

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

review/SKILL.md

@@ -206,6 +206,20 @@ If TODOS.md doesn't exist, skip this step silently.
 
 ---
 
+## Step 5.6: Documentation staleness check
+
+Cross-reference the diff against documentation files. For each `.md` file in the repo root (README.md, ARCHITECTURE.md, CONTRIBUTING.md, CLAUDE.md, etc.):
+
+1. Check if code changes in the diff affect features, components, or workflows described in that doc file.
+2. If the doc file was NOT updated in this branch but the code it describes WAS changed, flag it as an INFORMATIONAL finding:
+   "Documentation may be stale: [file] describes [feature/component] but code changed in this branch. Consider running `/document-release`."
+
+This is informational only — never critical. The fix action is `/document-release`.
+
+If no documentation files exist, skip this step silently.
+
+---
+
 ## Important Rules
 
 - **Read the FULL diff before commenting.** Do not flag issues already addressed in the diff.

review/SKILL.md.tmpl

@@ -124,6 +124,20 @@ If TODOS.md doesn't exist, skip this step silently.
 
 ---
 
+## Step 5.6: Documentation staleness check
+
+Cross-reference the diff against documentation files. For each `.md` file in the repo root (README.md, ARCHITECTURE.md, CONTRIBUTING.md, CLAUDE.md, etc.):
+
+1. Check if code changes in the diff affect features, components, or workflows described in that doc file.
+2. If the doc file was NOT updated in this branch but the code it describes WAS changed, flag it as an INFORMATIONAL finding:
+   "Documentation may be stale: [file] describes [feature/component] but code changed in this branch. Consider running `/document-release`."
+
+This is informational only — never critical. The fix action is `/document-release`.
+
+If no documentation files exist, skip this step silently.
+
+---
+
 ## Important Rules
 
 - **Read the FULL diff before commenting.** Do not flag issues already addressed in the diff.