feat: online verification, node removals, and knowledge browser

Adds claim-bound online evidence records and citation verification scripts,
node removal transport/adapter, retrieval benchmark and owner-review tooling,
GraphCanvas/SourceDetail knowledge browser UI, and the ingest handoff helper.
Bumps the agents/gewu pack to the online-verification branch.

schema/v1/records/ReadEnvelope.schema.json

@@ -313,6 +313,19 @@
       "title": "Data",
       "type": "array"
     },
+    "filtered_count": {
+      "anyOf": [
+        {
+          "minimum": 0,
+          "type": "integer"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "default": null,
+      "title": "Filtered Count"
+    },
     "index_revision": {
       "anyOf": [
         {