docs: fix the review findings on the hook-contract retirement

Why: a review of 4de5b6b and 3c5f6a6 found seven places that still
described the retired external hook contract as current, or that could
pass without checking anything.

Implementation Notes:
- gates.md: drop the "one caveat below" pointer; the caveat is gone.
- SIMPLIFICATION-AUDIT.md: the §7 note now says all but one entry is
  closed and lists 36 (4de5b6b) as struck. Finding 2's count chain gets
  a closing note: pre-push is 8 repo-authored hooks (10 reported).
- .pre-commit-config.yaml: the check-vale-style-sync comment points at
  case 32 (one-plugin narrowing guard), not the deleted case 33.
- ADR-0014: the retirement pointer now covers the ADR-0025 amendment
  above it too, naming case 33 and the exported hook IDs. ADR-0022 gets
  a reciprocal amended-by note on its check-release-needed comparison.
  Historical body text is unchanged.
- test-vale-wrap.sh case 32: property 3 fails when a class's corpus
  regex matches no tracked file, instead of passing vacuously after a
  layout move. The corpus regexes are now globals so a new Part D can
  point them at a missing layout and require that failure.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.pre-commit-config.yaml

@@ -167,7 +167,7 @@ repos:
       # assertions diffed skill-audit's Vale copy against agent-audit's; the
       # merge into factory-audit leaves one copy, so those are moot. The other
       # 11 moved into tests/test-vale-wrap.sh (case 0, cases 28-31, its
-      # Vale-absent skip, and case 33 for cross-manifest files: agreement),
+      # Vale-absent skip, and case 32 for the one-plugin narrowing guard),
       # which run-tests runs here at
       # pre-push, so do not re-add the hook to restore coverage. Do not
       # confuse its removal with check-scope-walkup-sync below, which survives: