distillation: fix 7 grounding bugs found by Kimi audit

Kimi For Coding (api.kimi.com, kimi-for-coding) ran a forensic audit on
distillation v1.0.0 with full file content. 7/7 flags verified real on
grep. Substrate now matches what v1.0.0 claimed: deterministic, no
schema bypasses, Rust tests compile.

Fixes:
- mode.rs:1035,1042  matrix_corpus Some/None -> vec![..]/vec![]; cargo
                     check --tests now compiles (was silently broken;
                     only bun tests were running)
- scorer.ts:30       SCORER_VERSION env override removed - identical
                     input now produces identical version stamp, not
                     env-dependent drift
- transforms.ts:181  auto_apply wall-clock fallback (new Date()) ->
                     deterministic recorded_at fallback
- replay.ts:378      recorded_run_id Date.now() -> sha256(recorded_at);
                     replay rows now reproducible given recorded_at
- receipts.ts:454,495  input_hash_match hardcoded true was misleading
                       telemetry; bumped DRIFT_REPORT_SCHEMA_VERSION 1->2,
                       field is now boolean|null with honest null when
                       not computed at this layer
- score_runs.ts:89-100,159  dedup keyed only on sig_hash made
                            scorer-version bumps invisible. Composite
                            sig_hash:scorer_version forces re-scoring
- export_sft.ts:126  (ev as any).contractor bypass emitted "<contractor>"
                     placeholder for every contract_analyses SFT row.
                     Added typed EvidenceRecord.metadata bucket;
                     transforms.ts populates metadata.contractor;
                     exporter reads typed value

Verification (all green):
  cargo check -p gateway --tests   compiles
  bun test tests/distillation/     145 pass / 0 fail
  bun acceptance                   22/22 invariants
  bun audit-full                   16/16 required checks

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

scripts/distillation/score_runs.ts

@@ -86,6 +86,17 @@ function gitDirty(root: string): boolean {
   return r.status === 0 && r.stdout.trim().length > 0;
 }
 
+// Composite dedup key — `sig_hash:scorer_version`. Keying on sig_hash
+// alone made scorer-rule bumps invisible: a bumped SCORER_VERSION
+// produced different scoring categories, but pre-existing rows on disk
+// (with the OLD version) still matched the new sig_hash and the new
+// scoring was silently skipped. Compositing version forces re-scoring
+// when the version changes. Caller tags `scorer_version` on the
+// ScoredRun row, which we read alongside sig_hash.
+function dedupKey(sig_hash: string, scorer_version: string): string {
+  return `${sig_hash}:${scorer_version}`;
+}
+
 function loadSeenHashes(out_path: string): Set<string> {
   const seen = new Set<string>();
   if (!existsSync(out_path)) return seen;
@@ -93,7 +104,9 @@ function loadSeenHashes(out_path: string): Set<string> {
     if (!line) continue;
     try {
       const row = JSON.parse(line);
-      if (row?.provenance?.sig_hash) seen.add(row.provenance.sig_hash);
+      const sh = row?.provenance?.sig_hash;
+      const sv = row?.scorer_version;
+      if (sh && sv) seen.add(dedupKey(sh, sv));
     } catch { /* malformed — ignore */ }
   }
   return seen;
@@ -156,11 +169,12 @@ async function processEvidenceFile(
     }
 
     const scored = await buildScoredRun(ev.value as EvidenceRecord, out_relpath, i, opts.recorded_at);
-    if (seen.has(scored.provenance.sig_hash)) {
+    const key = dedupKey(scored.provenance.sig_hash, scored.scorer_version);
+    if (seen.has(key)) {
       result.rows_deduped++;
       continue;
     }
-    seen.add(scored.provenance.sig_hash);
+    seen.add(key);
 
     const sv = validateScoredRun(scored);
     if (!sv.valid) {