Adds a comprehensive 'External audit documents' section to the reviewer index:
- groups all 12 audits (correctness, API/perf/packaging, robustness)
- surfaces G0 (porting rights) as the cross-cutting release blocker
- records the decisions taken: coverage gate 80/70/90, API naming A1-A5
(A1-A3 implemented in PR #36, A4-A5 deferred pending G0/G1)
- points a new session at the low-risk quick-win findings
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>