feat(agent): make ingestion preparation reproducible

contracts/service-v1.json

@@ -1,6 +1,6 @@
 {
   "api_version": "v1",
-  "catalog_sha256": "8c721bdb8b78e50606d4d479d716076f1f609ecb908fb32c10b7eaccc06eb04e",
+  "catalog_sha256": "872d3bf0647f9ec1a3f0e6d3d994fe03076b78bb7468cf3a24218d4b8ca8b075",
   "contract_id": "gewu.service.v1",
   "contract_version": 1,
   "operations": [
@@ -156,6 +156,14 @@
         "mcp"
       ]
     },
+    {
+      "capability": "proposal:evaluate",
+      "mutates_knowledge": false,
+      "name": "proposal_prepare",
+      "transports": [
+        "mcp"
+      ]
+    },
     {
       "capability": "proposal:evaluate",
       "mutates_knowledge": false,
@@ -1220,6 +1228,23 @@
       },
       "name": "proposal_submit"
     },
+    {
+      "description": "Fill canonical evidence and payload digests without storing the proposal.",
+      "input_schema": {
+        "properties": {
+          "proposal_json": {
+            "title": "Proposal Json",
+            "type": "string"
+          }
+        },
+        "required": [
+          "proposal_json"
+        ],
+        "title": "proposal_prepareArguments",
+        "type": "object"
+      },
+      "name": "proposal_prepare"
+    },
     {
       "description": "Evaluate one bounded proposal without storing or publishing it.",
       "input_schema": {