feat(agent): add online verification and governing-answer citations

Claim-bound online verification observations with URL provenance, exact
answer-basis references for citation-free governing-rule answers, and an
explicit operator identity handoff before source transfer. Bounds resumed
work by learning unit and refreshes pack manifest/contracts.

contracts/schemas/SearchRequest.schema.json

@@ -161,6 +161,11 @@
       "title": "Domain",
       "type": "array"
     },
+    "include_evidence": {
+      "default": true,
+      "title": "Include Evidence",
+      "type": "boolean"
+    },
     "limit": {
       "default": 20,
       "maximum": 50,