docs(reviewer): mark S2 (I1/H1/N7) done in the plan + audit banners

Update finding-orchestration.md (master table I1/H1/N7 → ✅, S2 session marked
done with the original plan folded into a <details>), README headline cells +
next-batch pointer (now S3), and the test-coverage / numerical-stability audit
banners.  S2 was implemented directly by Opus in the warm post-refactor session
(commit 90e966a); 301/301 tests green.

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

doc/reviewer/README.md

@@ -60,7 +60,7 @@ S2–S6.
 | [`external-audit-2026-05-30.md`](external-audit-2026-05-30.md) | Correctness bugs | 3 findings (face_energy, Gauss–Bonnet, cotangent doc) — **all resolved** |
 | [`java-port-audit.md`](java-port-audit.md) | Java→C++ math fidelity | line-by-line port anomalies — mostly resolved |
 | [`java-ignore-crossvalidation.md`](java-ignore-crossvalidation.md) | `@Ignore` cross-validation | which Java tests were intentionally skipped and why |
-| [`numerical-stability-audit-2026-05-31.md`](numerical-stability-audit-2026-05-31.md) | FP robustness | **N3/N4/N5/N6 ✅** (clamp mode, named constants, Kahan area); **N1 ✅\*** subsumed by B1 block-FD; **N2/N7 open** |
+| [`numerical-stability-audit-2026-05-31.md`](numerical-stability-audit-2026-05-31.md) | FP robustness | **N3/N4/N5/N6 ✅** (clamp mode, named constants, Kahan area), **N7 ✅** (conditioning diag, S2); **N1 ✅\*** subsumed by B1; **N2 open** |
 | [`math-derivation-citation-audit-2026-05-31.md`](math-derivation-citation-audit-2026-05-31.md) | Derivations & citations | **M1/M2/M4 ✅** (refs + year + citation format); **M3 open**, **M5 needs expert** |
 
 ## API, performance & packaging
@@ -76,7 +76,7 @@ S2–S6.
 
 | Document | Focus | Headline |
 |---|---|---|
-| [`test-coverage-error-handling-audit-2026-05-31.md`](test-coverage-error-handling-audit-2026-05-31.md) | Coverage + error handling | **C1/C2/C3 ✅**, **I2/I3/I4 ✅**, **H2 ✅** (newton_core); **I1/I5/H1/H3/H4/H5 open**; gate in ramp-up until I5 |
+| [`test-coverage-error-handling-audit-2026-05-31.md`](test-coverage-error-handling-audit-2026-05-31.md) | Coverage + error handling | **C1/C2/C3 ✅**, **I2/I3/I4 ✅**, **H2 ✅** (newton_core), **I1/H1 ✅** (status enum, S2); **I5/H3/H4/H5 open**; gate in ramp-up until I5 |
 | [`input-validation-audit-2026-05-31.md`](input-validation-audit-2026-05-31.md) | Malformed input | **V1/V2/V3/V4 ✅** (NaN/Inf guard + JSON/XML error handling); **V5/V6 open** (polish) |
 | [`thread-safety-audit-2026-05-31.md`](thread-safety-audit-2026-05-31.md) | Concurrency | no mutable static state (good); same-mesh concurrency contract **still undocumented (open, S4)** |
 
@@ -92,6 +92,10 @@ See [`finding-orchestration.md`](finding-orchestration.md) for the full plan.
 - **🔍 Opus review:** all Sonnet/Haiku commits validated (value-identity, error
   handling, coverage-gate logic, alias forwarding) — all correct.
 
+**Session 2 (Opus, same day):** I1 (NewtonStatus enum) + H1 (iteration count) +
+N7 (`sparse_qr_fallback_used` / `min_ldlt_pivot` diagnostics) — done directly in
+the warm post-refactor session, commit `90e966a`, 301/301 tests green.
+
 ### Decisions standing
 - **Coverage gate:** 80 % line / 70 % branch / 90 % function. Script now measures
   honestly (C2 ✅); gate is in **ramp-up** (`SKIP_COVERAGE_GATE=1`) until **I5**
@@ -107,8 +111,8 @@ See [`finding-orchestration.md`](finding-orchestration.md) for the full plan.
 Open the relevant audit, pick a finding, follow its "Fix" + "Acceptance criteria".
 Build/verify with the commands in that document's header. **The Session-1 quick-win
 batch (B1, B3, C1, C2, V3, …) is done** — for what to pick up next, follow the
-session plan in [`finding-orchestration.md`](finding-orchestration.md): the next
-pending batch is **S2** (I1 + H1 + N7, Sonnet→Opus review).
+session plan in [`finding-orchestration.md`](finding-orchestration.md): **S1+S2
+done**; the next pending batch is **S3** (H3/H4/H5 + V5/V6, Sonnet→Opus review).
 
 ## When to send to the reviewer