fix: harden Codex hook finalization

packages/casan-harness/scripts/python/agentic_bridge.py

@@ -857,14 +857,39 @@ def op_finalize(req):
     # summary as the closing verification control.
     reasons = []
     if req.get("assistant_summary"):
-        ok, why = h4_scan(req.get("assistant_summary"), "output")
-        add_evidence(rec, "H3/H7", "finalize-verify", "allow" if ok else "flag", why)
-        if not ok:
+        h4 = h4_scan(req.get("assistant_summary"), "output")
+        if h4 == "ok":
+            add_evidence(
+                rec, "H3/H7", "finalize-verify", "allow", "h4_ok")
+        elif h4 == "unavailable":
+            # An output that could not be scanned must never be certified.
+            # Match begin/pre-tool graceful degradation: keep the developer
+            # workflow available, but make the missing control explicit.
+            rec["integration_mode"] = "observed_only"
+            rec["certification_strength"] = "observed_only"
+            add_evidence(
+                rec, "H3/H7", "finalize-verify", "degraded",
+                "gate_unavailable_no_bash")
+            reasons.append("output_gate_unavailable")
+        else:
+            # A policy block or timeout is fail-closed for certification.
+            # Treat unknown statuses the same way so a future contract change
+            # cannot silently certify an unverified output.
+            why = {
+                "blocked": "h4_blocked",
+                "timeout": "h4_internal_timeout",
+            }.get(h4, "h4_unknown_status")
+            add_evidence(
+                rec, "H3/H7", "finalize-verify", "flag", why)
             reasons.append("output_flagged:%s" % why)
 
     # Certification decision.
     strength = rec.get("certification_strength", "observed_only")
     certified = True
+    if reasons:
+        # Any closing output-verification failure above is certification-fatal,
+        # even when every earlier admission/tool control succeeded.
+        certified = False
     if enforcement_mode() != "enforce":
         certified = False
         reasons.append("observe_mode")