app-server: Replay pending item requests on thread/resume (#12560)

Replay pending client requests after `thread/resume` and emit resolved
notifications when those requests clear so approval/input UI state stays
in sync after reconnects and across subscribed clients.

Affected RPCs:
- `item/commandExecution/requestApproval`
- `item/fileChange/requestApproval`
- `item/tool/requestUserInput`

Motivation:
- Resumed clients need to see pending approval/input requests that were
already outstanding before the reconnect.
- Clients also need an explicit signal when a pending request resolves
or is cleared so stale UI can be removed on turn start, completion, or
interruption.

Implementation notes:
- Use pending client requests from `OutgoingMessageSender` in order to
replay them after `thread/resume` attaches the connection, using
original request ids.
- Emit `serverRequest/resolved` when pending requests are answered
or cleared by lifecycle cleanup.
- Update the app-server protocol schema, generated TypeScript bindings,
and README docs for the replay/resolution flow.

High-level test plan:
- Added automated coverage for replaying pending command execution and
file change approval requests on `thread/resume`.
- Added automated coverage for resolved notifications in command
approval, file change approval, request_user_input, turn start, and turn
interrupt flows.
- Verified schema/docs updates in the relevant protocol and app-server
tests.

Manual testing:
- Tested reconnect/resume with multiple connections.
- Confirmed state stayed in sync between connections.

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

@@ -0,0 +1,30 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "definitions": {
+    "RequestId": {
+      "anyOf": [
+        {
+          "type": "string"
+        },
+        {
+          "format": "int64",
+          "type": "integer"
+        }
+      ]
+    }
+  },
+  "properties": {
+    "requestId": {
+      "$ref": "#/definitions/RequestId"
+    },
+    "threadId": {
+      "type": "string"
+    }
+  },
+  "required": [
+    "requestId",
+    "threadId"
+  ],
+  "title": "ServerRequestResolvedNotification",
+  "type": "object"
+}