feat(real-world-vfc-slice): add labeled OpenSSL/Firefox/Chromium/curl pair corpus

Harvest 176 isolated vuln-vs-fix functions (109 CVEs, 352 training rows)
into benchmarks/pairs/vfc with provenance and a JSONL training manifest.
Score the slice as an honesty dashboard (ousast pairs --slice vfc);
keep the pair gate on the local fixtures only.

.kiro/specs/real-world-vfc-slice/spec.json

@@ -0,0 +1,22 @@
+{
+  "feature_name": "real-world-vfc-slice",
+  "created_at": "2026-09-04T13:19:17Z",
+  "updated_at": "2026-09-04T13:40:00Z",
+  "language": "en",
+  "phase": "implementation",
+  "approvals": {
+    "requirements": {
+      "generated": true,
+      "approved": true
+    },
+    "design": {
+      "generated": true,
+      "approved": true
+    },
+    "tasks": {
+      "generated": true,
+      "approved": true
+    }
+  },
+  "ready_for_implementation": true
+}