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>

STATE_OF_PLAY.md

@@ -270,6 +270,7 @@ a steady state. Future items will land here as production triggers fire.
 | (close-2 full) | **OPEN #2 fully ported** (2026-05-01): `SynthesizeSft` + `LoadEvidenceByRunID` + `buildInstruction` ported byte-for-byte from `scripts/distillation/export_sft.ts`. All 8 source-class instruction templates (scrum_reviews / mode_experiments / auto_apply / audits / observer_reviews / contract_analyses / outcomes / default) match Rust output exactly so a/b validation between runtimes can diff JSONL byte-for-byte. `ExportSft` writes to `data/distilled/sft/sft_export.jsonl`. 5 additional tests including per-source-class template verification, extraction-rejection, empty-text-rejection, context-assembly, end-to-end fixture write. |
 | (close-2 lineage) | **Audit-baselines lineage ported** (2026-05-01): `internal/distillation/audit_baseline.go` mirrors Rust `audit_full.ts`'s LoadBaseline/AppendBaseline/buildDriftTable. `LoadLastBaseline` reads the most recent JSON line from `data/_kb/audit_baselines.jsonl`; `AppendBaseline` appends append-only with bufio. `BuildAuditDriftTable` flags drift `>20%` (configurable); zero-baseline and new-metric edge cases handled (no division-by-zero, no false-stable on zero→nonzero). `FormatAuditDriftTable` for stdout dumps. Generic on metric names so callers running both runtimes can pin Rust-compat names (`AuditBaselineRustCompat` constant lists them). 13 tests including last-line-wins, trailing-blank-tolerance, malformed-line-errors, threshold-boundary, zero-baseline-handling, sort-stability. |
 | (scrum) | 3-lineage scrum on `434f466..0d4f033` (post_role_gate_v1). Convergent finding (Opus + Kimi): `DecodeIndex` lost nil-meta items across persistence. **Fixed** by bumping envelope version 1→2 with explicit `IDs []string` field; v1 envelopes still load via meta-key fallback. Opus-only real bugs also actioned: `handleMerge` non-`ErrIndexNotFound` nil-deref, `mathLog` dead wrapper removed, bubble sort → `sort.Slice`. False positives rejected after verification (Kimi rollback misreading + Opus stale-comment claim). 2 new regression tests lock the v2 round-trip + v1 backward-compat. Disposition: `reports/scrum/_evidence/2026-05-01/verdicts/post_role_gate_v1_disposition.md`. |
+| (audit-full port) | **Audit-FULL pipeline** (phases 0/3/4) ported from `scripts/distillation/audit_full.ts`. `internal/distillation/audit_full.go` + `cmd/audit_full` CLI. 6 ported required-check classes; 4 phases (1, 2, 5, 6, 7) deferred — depend on broader Rust pieces (materializer / replay / run-summaries) not yet ported. **Cross-runtime byte-equal verdict on live data**: Go-side audit-full against `/home/profit/lakehouse` produced p3_*/p4_* metrics IDENTICAL to the last Rust-emitted `audit_baselines.jsonl` entry (all 8 metrics match: 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 new tests + the live-data probe captured in `reports/cutover/audit_full_go_vs_rust.md`. |
 | (close-3) | **OPEN #3: distribution drift via PSI** — `internal/drift/drift.go`: `ComputeDistributionDrift` returns Population Stability Index + verdict tier (stable < 0.10, minor 0.10–0.25, major ≥ 0.25). Equal-width bucketing over combined min/max range, epsilon-clamping for empty buckets, per-bucket breakdown for drilldown. 7 new tests including identical-is-stable, hard-shift-is-major, moderate-detected-not-stable, empty-inputs-safe, all-identical-safe, bucket-counts-conserved, num-buckets-clamping. |
 | (close-4) | **OPEN #4: ops nice-to-haves** — (a) Real-time wall-clock for stress harness: per-phase elapsed time logged to stdout as it runs (`[stress] phase NAME starting (T+12.3s)` + `[stress] phase NAME done — 8.5s (T+20.8s)`); `Output.PhaseTimings` + `Output.TotalElapsedMs` written to JSON; (b) chatd fixture-mode S3 mock + (c) liberal-paraphrase calibration: not actioned — no fired trigger yet, would be speculative. Documented as deferred-until-need rather than ignored. |