Include spawn agent model metadata in app-server items (#14410)

- add model and reasoning effort to app-server collab spawn items and
notifications
- regenerate app-server protocol schemas for the new fields

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/app-server-protocol/schema/json/v2/ThreadForkResponse.json

@@ -1349,6 +1349,13 @@
               "description": "Unique identifier for this collab tool call.",
               "type": "string"
             },
+            "model": {
+              "description": "Model requested for the spawned agent, when applicable.",
+              "type": [
+                "string",
+                "null"
+              ]
+            },
             "prompt": {
               "description": "Prompt text sent as part of the collab tool call, when available.",
               "type": [
@@ -1356,6 +1363,17 @@
                 "null"
               ]
             },
+            "reasoningEffort": {
+              "anyOf": [
+                {
+                  "$ref": "#/definitions/ReasoningEffort"
+                },
+                {
+                  "type": "null"
+                }
+              ],
+              "description": "Reasoning effort requested for the spawned agent, when applicable."
+            },
             "receiverThreadIds": {
               "description": "Thread ID of the receiving agent, when applicable. In case of spawn operation, this corresponds to the newly spawned agent.",
               "items": {