docs+tooling: doc-freshness gate, documentation-pass policy, token-hygiene

Refresh CLAUDE.md for v0.10.0 (3 CI jobs incl. disabled test-cgal,
compile-time option matrix, reviewer/pages docs, agentic + token-hygiene
workflow patterns) and condense the historical Phase-8/audit logs to
pointers.

Add the documentation-pass process so the single-source-of-truth rules
stay enforced:
  * scripts/quality/check-doc-freshness.sh — string-only drift gate
    (version/date across CITATION/CHANGELOG/CLAUDE, doc-map count), <1 s,
    registered in run-all.sh + quality README.
  * doc/release-policy.md — "Documentation passes" subsection (triggers +
    docs:sync rule); fix stale Phase-milestone mapping (v0.10.0 was
    reviewer-ready, 9c→v0.11.0) and the test-cgal CI mention.

Add shared Claude config (un-ignore the two files only):
  * .claude/settings.json — permission allowlist for safe repo commands.
  * .claude/token-hygiene.md — Tier-3 cache-discipline user guide that
    CLAUDE.md instructs Claude to remind the user about.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.gitignore

@@ -25,8 +25,10 @@ Testing/
 *.user
 *.suo
 
-# Claude Code worktrees
-.claude/
+# Claude Code worktrees + local/session data (but track shared project config)
+.claude/*
+!.claude/settings.json
+!.claude/token-hygiene.md
 
 # Doxygen output
 doc/doxygen/