docs(reviewer): update audit status + add finding-orchestration plan

Session 1 (2026-05-31) resolved 26 findings across Sonnet/Haiku/Opus; 298/298
CGAL tests green.  Bring the audit docs in line with reality:

- README.md: G0 banner now records that the original authors were contacted by
  email about porting/relicensing rights (awaiting reply); headline-status cells
  updated per finding; new "Session 1 — implemented" record; link to the plan.
- Per-audit resolution banners (api-performance, numerical-stability,
  input-validation, test-coverage, math-citation, thread-safety) + G0-blocked
  banners (cgal-submission, dependency-license).
- NEW finding-orchestration.md: the meta-plan mapping every finding to a session,
  an implementing model (Haiku/Sonnet/Opus by the "how much must be understood"
  rule), and an Opus review gate after each implementation session.  Records S1
  (done) and lays out S2–S6 so the next session can be picked up cold.

Docs only — no code change.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

doc/reviewer/thread-safety-audit-2026-05-31.md

@@ -9,6 +9,11 @@ documented? Currently undocumented everywhere.
 
 Status legend: 🔴 Critical · 🟡 Important · 🔵 Polish
 
+> **Status (2026-05-31):** no code change needed (no mutable static state — good).
+> The one open item is **documenting the same-mesh concurrency contract** —
+> scheduled **S4** (Haiku→Opus review) in
+> [`finding-orchestration.md`](finding-orchestration.md).
+
 > **Good news up front:** a scan for mutable function-local `static` variables (the
 > classic hidden-shared-state hazard) found **none**. All `static` in the headers are
 > stateless factory/accessor functions (`MobiusMap::identity`,