spec+docs(search-with-proof): record first cluster demonstration + fixed-side negative [skip ci]

Feed the milestone back into the spec and steering. HANDOFF: the open "first demonstrated"
question is RESOLVED -- xiaomusic (path, prefix-check-bypass) demonstrated on the vulnerable
side (3/3 affected, 0/3 safe) and the blind fixed-side search produced 0 false proofs; pair
total $1.22. Records the six-fix chain that enabled it (parity, verify-time-only, fair-share
budget, served-root guidance, oracle prefix-bypass coverage, control-signal feedback) plus the
keystone. tasks.md: implementation note; pilot (6.2/6.3) in progress. spec.json: pilot status.
safety-net steering: proof-based BLOCK mechanism reached first execution-backed demonstration
(feasibility-pilot scope, not release readiness; pilot exit + 73-negative qualification open;
classifier stays triage). search README: status note. Payload-free; demos/boards stay gitignored.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

.kiro/specs/search-with-proof/spec.json

@@ -1,7 +1,7 @@
 {
   "feature_name": "search-with-proof",
   "created_at": "2026-10-05T12:00:00Z",
-  "updated_at": "2026-10-05T15:30:00Z",
+  "updated_at": "2026-10-07T13:30:00Z",
   "language": "en",
   "phase": "tasks-generated",
   "approvals": {
@@ -18,5 +18,12 @@
       "approved": false
     }
   },
-  "ready_for_implementation": false
-}
+  "ready_for_implementation": false,
+  "pilot": {
+    "status": "in_progress",
+    "first_cluster_demonstration": "2026-10-07",
+    "pair": "xiaomusic (path, prefix-bypass)",
+    "false_proofs": 0,
+    "exit_remaining": "path family >=5 demonstrations / 0 false proofs (Req 6.2), then >=73-negative BLOCK qualification (Req 6.3)"
+  }
+}