corpus: align determinability key with the schema column

The truth files used `determinableFromResponseDocument`; the schema column
and gateEvaluableFromResponse() use `determinableFromResponse`. A silent
name drift means the flag reads as its default (true), and R-B6C — "two bid
copies submitted", which no response document can ever establish — starts
failing bidders on a packaging detail.

Renamed in rfp.truth.json and validate-responses.py, and added the mirror
check to validate-truth.py so the drift cannot recur unnoticed:

  gates 13, evaluable from the response 12, excluded 1
    excluded: R-B6C  Two bid copies submitted.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

corpus/validate-truth.py

@@ -77,6 +77,22 @@ for cid in sec:
     if cid not in crit: errs.append(f"bindingMechanism section -> unknown criterion {cid}")
 
 gates = [r for r in t['requirements'] if r['kind'] == 'mandatory_gate']
+
+# Mirrors gateEvaluableFromResponse() in src/scoring/routing.ts. The key read
+# here is the SCHEMA COLUMN NAME on purpose — the two names drifted once, and a
+# silent drift means the flag reads as its default and a bidder is disqualified
+# over something no document could have proven.
+evaluable = [r for r in gates if r.get('determinableFromResponse', True)]
+excluded  = [r for r in gates if not r.get('determinableFromResponse', True)]
+print(f"  ok   gates {len(gates)}, evaluable from the response {len(evaluable)}, "
+      f"excluded {len(excluded)}")
+for r in excluded:
+    print(f"       excluded: {r['id']:14} {r['text'][:50]}")
+for r in t['requirements']:
+    if r.get('determinableFromResponse') is False and r['kind'] != 'mandatory_gate':
+        warns.append(f"{r['id']} is not determinable but is not a gate — the flag "
+                     f"only changes gate evaluation, so this has no effect")
+
 kinds = {}
 for r in t['requirements']: kinds[r['kind']] = kinds.get(r['kind'], 0) + 1
 print(f"\n  requirements {len(t['requirements'])}  criteria {len(t['criteria'])}  knownMisses {len(t['knownMisses'])}")