claim_parser: history/proof claims join empirical class

PR #9's 4 block findings were all from commit message references to
prior work ("on PR #8", "the proven X", "flipping across N runs").
The cloud reviewer correctly said "the current diff does not prove
that", but the claim was never about the current diff — the proof
lives in the referenced prior PR or test run.

Extended EMPIRICAL_PATTERNS to cover two shared classes:

  1. Runtime metrics (existing) — "58 cloud calls", "306s elapsed"
  2. History/proof refs (new) — "verified on PR #8", "was flipping
     across 9 runs", "the proven escalation ladder", "previously
     observed in PR #6", "tested against commit abc1234"

Both skip diff-verification for the same reason: the proof is outside
the diff. Folded into the existing bucket rather than adding a new
strength tier — the skip discipline is identical so there's no value
in splitting them.

Unit-tested on PR #9's actual failing lines: all 5 historical claims
now classify as empirical; fresh claims like "Phase 45 shipped" stay
strong; pure implementation descriptions ("implements deterministic
classification") still don't match (expected — they're not
claims, they're restatements).

auditor/claim_parser.ts

@@ -51,11 +51,20 @@ const WEAK_PATTERNS: RegExp[] = [
 
 // Empirical claims: runtime measurements / observed outcomes that can't
 // be verified from a diff (only from the actual run that produced
-// them). Example: "6/6 iterations complete, 58 cloud calls, 306s
+// them). Classifying as empirical lets the inference check skip
-// end-to-end" — true, but only the test's own summary.json can
-// confirm it. Classifying as empirical lets the inference check skip
 // diff-verification and saves the ladder for falsifiable claims.
+//
+// Two classes share this bucket because they share the skip discipline:
+//
+//   1. Runtime metrics    — "58 cloud calls", "306s end-to-end"
+//   2. History/proof refs — "verified on PR #8", "was flipping across runs"
+//
+// Both are assertions about state outside the current diff. The cloud
+// would flag them as "not backed" — but that's a false positive: the
+// proof lives in the referenced run, prior commit, or test output, not
+// in the added lines the cloud is reading.
 const EMPIRICAL_PATTERNS: RegExp[] = [
+  // ─── Runtime metrics ───
   // Iteration / attempt counts: "6/6 iterations", "attempt 5", "accepted on attempt 3"
   /\b\d+\s*\/\s*\d+\s+(iterations?|attempts?|cycles?|runs?|shards?)\b/i,
   /\b(accepted|resolved|converged)\s+on\s+attempt\s+\d+\b/i,
@@ -66,6 +75,27 @@ const EMPIRICAL_PATTERNS: RegExp[] = [
   // "escalated through N tiers", "N distinct models"
   /\bescalated\s+through\s+\d+\b/i,
   /\b\d+\s+distinct\s+(model|tier)s?\b/i,
+
+  // ─── History / proof references ───
+  // "verified on PR #8", "verified end-to-end on PR 8", "tested against PR #4"
+  /\bverified\s+(?:end[- ]to[- ]end\s+)?(?:on|against|in)\s+(?:PR|commit|prior|the\s+\w+\s+audit)\s*#?\w*/i,
+  /\btested\s+(?:against|in|on)\s+(?:PR|commit|prior)\s*#?\w*/i,
+  // Direct PR/commit references: "PR #8", "on PR 9", "from commit abc123"
+  /\b(?:on|from|in|via|per)\s+PR\s*#?\d+\b/i,
+  /\b(?:from|in|per|against)\s+commit\s+[0-9a-f]{6,}/i,
+  // Observational descriptions of prior behavior: "was flipping", "was X before", "previously observed"
+  /\b(?:was|were)\s+(?:flipping|drifting|inconsistent|non[- ]deterministic|creeping)\b/i,
+  /\bpreviously\s+(?:observed|flagged|reported|seen|landed)\b/i,
+  /\bused\s+to\s+(?:flip|fail|flag|reject|block)\b/i,
+  /\bobserved\s+(?:in|during|on|across)\s+(?:PR|prior|\d+\s+(?:runs?|audits?))/i,
+  // "flipping/drifting across N runs" — historical variance description
+  /\b(?:flipping|drifting|varying|oscillating)\s+across\s+(?:\d+\s+)?(?:runs?|audits?|iterations?)\b/i,
+  // "the proven X" referring to prior work (proven is a STRONG pattern
+  // but in context "the proven FOO" is usually a historical reference,
+  // not a fresh claim). We catch it here so the empirical skip wins.
+  /\bthe\s+proven\s+(?:escalation\s+ladder|pipeline|flow|loop|tier|path)/i,
+  // "from the 9-run test", "across the 5-run validation"
+  /\b(?:from|across|in|during)\s+the\s+\d+[- ]run\s+(?:test|validation|probe|experiment)/i,
 ];
 
 export interface ParsedClaims {