distillation: audit-FULL pipeline port (phases 0/3/4) — cross-runtime metric parity verified

Ports the metric-collection passes from scripts/distillation/audit_full.ts.
The substrate that PRODUCES audit_baselines.jsonl entries — the
half OPEN #2 left as "deferred to next wave" after the read/write
substrate landed in ca142b9.

Phase coverage:
  Phase 0 (file presence)             ported
  Phase 1 (schema validators)         skipped (Go's `go test` covers it)
  Phase 2 (materializer dry-run)      deferred (Go materializer not yet ported)
  Phase 3 (scored-runs distribution)  ported
  Phase 4 (contamination firewall)    ported
  Phase 5 (receipts validation)       deferred (Go run-summary JSON not yet emitted)
  Phase 6 (replay sanity)             deferred (Go replay tool not ported)
  Phase 7 (run summary lineage)       deferred (same)

Cross-runtime parity verified end-to-end:
  Go-side audit-full against /home/profit/lakehouse produced
  metrics IDENTICAL to the last Rust-emitted audit_baselines.jsonl
  entry. All 8 ported metrics match byte-for-byte:
    p3_accepted=386, p3_partial=132, p3_rejected=57, p3_human=480,
    p4_sft_rows=353, p4_rag_rows=448, p4_pref_pairs=83, p4_total_quarantined=1325
  6/6 required checks pass on live data.

Components:
- internal/distillation/audit_full.go: PhaseCheck struct (mirrors
  Rust shape), PhaseCheckReport aggregation, RunAuditFull
  orchestrator, auditPhase0/3/4 implementations, FormatAuditFullReport
  Markdown writer.
- cmd/audit_full/main.go: CLI binary with -root, -out, -json,
  -append-baseline flags. Operators run "./bin/audit_full
  -append-baseline" to grow the longitudinal log alongside the
  Rust pipeline (entries are interchangeable — same envelope shape).
- 6 new tests: empty-root failure handling, full-fixture clean PASS
  (locks all 8 metrics + all 6 required checks), SFT firewall
  contamination detection, preference self-pair detection, sig_hash
  regex correctness (rejects wrong-length + uppercase), Markdown
  formatter smoke.

Live-data probe captured at reports/cutover/audit_full_go_vs_rust.md
(linked from reports/cutover/SUMMARY.md). Same shape as the
audit_baselines round-trip evidence — both Go-side ports of the
distillation surface are now validated against real Rust data, not
just fixtures.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

reports/cutover/SUMMARY.md

@@ -8,6 +8,7 @@ what's safe to flip. Append a row when a new endpoint clears parity.
 | `embed` (forced v1)     | 2026-04-30 | `/ai/embed`              | `/v1/embed`              | ✅ PASS 5/5 cos=1.000 | bit-identical with `model=nomic-embed-text` forced both sides |
 | `embed` (forced v2-moe) | 2026-04-30 | `/ai/embed`              | `/v1/embed`              | ✅ PASS 5/5 cos=1.000 | bit-identical with `model=nomic-embed-text-v2-moe` forced both sides — both Ollamas have the model |
 | `audit_baselines.jsonl` | 2026-05-01 | `data/_kb/audit_baselines.jsonl` | `internal/distillation` `LoadLastBaseline` / `AppendBaseline` / `BuildAuditDriftTable` | ✅ PASS round-trip | Live Rust file (7 entries) parses + round-trips byte-equal; lineage drift table fires correctly on zero-baseline metrics. See `audit_baselines_roundtrip.md`. |
+| `audit-FULL` (phases 0/3/4) | 2026-05-01 | `scripts/distillation/audit_full.ts` | `cmd/audit_full` + `internal/distillation` `RunAuditFull` | ✅ PASS metric-equal | Go-side run against live Rust root: all 8 ported metrics (p3_*, p4_*) byte-equal to the last Rust-emitted `audit_baselines.jsonl` entry. 6/6 required checks pass. 4 phases (1, 2, 5, 6, 7) deferred — depend on broader Rust-side pieces (materializer / replay / run-summaries) not yet ported. See `audit_full_go_vs_rust.md`. |
 
 ## Wire-format drift catalog