Include originating item IDs in MCP request metadata (#40866)

## What changed

- Add the originating Responses item ID to MCP tool request metadata as
  `_meta.itemId`.
- Preserve the initiating `exec` item ID across code-mode cells so nested MCP
  calls carry the same origin.

## Testing

- Cover metadata generation for direct and code-mode MCP tool calls.

GitOrigin-RevId: 1161cac64f1cc3a6d4dac4368e63804bd9d2c417

codex-rs/core/tests/suite/code_mode.rs

@@ -1209,14 +1209,11 @@ async fn code_mode_only_guides_all_tools_search_and_calls_deferred_app_tools() -
 
     let server = responses::start_mock_server().await;
     let apps_server = AppsTestServer::mount_searchable(&server).await?;
-    let resp_mock = responses::mount_sse_once(
-        &server,
-        sse(vec![
-            ev_response_created("resp-1"),
-            ev_custom_tool_call(
-                "call-1",
-                "exec",
-                r#"
+    let originating_item_id = "ctc_code_mode_origin";
+    let mut exec_call = ev_custom_tool_call(
+        "call-1",
+        "exec",
+        r#"
 const tool = ALL_TOOLS.find(
   ({ name }) => name === "mcp__codex_apps__calendar_timezone_option_99"
 );
@@ -1231,7 +1228,13 @@ if (!tool) {
   }));
 }
 "#,
-            ),
+    );
+    exec_call["item"]["id"] = serde_json::json!(originating_item_id);
+    let resp_mock = responses::mount_sse_once(
+        &server,
+        sse(vec![
+            ev_response_created("resp-1"),
+            exec_call,
             ev_completed("resp-1"),
         ]),
     )
@@ -1325,6 +1328,13 @@ if (!tool) {
             "text": "called calendar_timezone_option_99 for  at  with ",
         })
     );
+    let apps_tool_calls = recorded_apps_tool_calls(&server).await;
+    assert!(
+        apps_tool_calls.iter().any(|call| {
+            call.pointer("/params/_meta/itemId") == Some(&serde_json::json!(originating_item_id))
+        }),
+        "the nested MCP call should inherit its code cell's originating Responses item"
+    );
 
     Ok(())
 }

codex-rs/core/tests/suite/mcp_turn_metadata.rs

@@ -170,6 +170,7 @@ async fn approved_mcp_tool_call_metadata_records_prior_user_input_request(
     let server = start_mock_server().await;
     let apps_server = AppsTestServer::mount(&server).await?;
     let call_id = "calendar-call-approval";
+    let originating_item_id = "fc_calendar_approval_origin";
     let calendar_args = serde_json::to_string(&json!({
         "title": "Lunch",
         "starts_at": "2026-03-10T12:00:00Z"
@@ -196,14 +197,16 @@ async fn approved_mcp_tool_call_metadata_records_prior_user_input_request(
             ev_completed("resp-permissions"),
         ]));
     }
+    let mut calendar_call = ev_function_call_with_namespace(
+        call_id,
+        SEARCH_CALENDAR_NAMESPACE,
+        SEARCH_CALENDAR_CREATE_TOOL,
+        &calendar_args,
+    );
+    calendar_call["item"]["id"] = json!(originating_item_id);
     response_sequence.push(sse(vec![
         ev_response_created("resp-1"),
-        ev_function_call_with_namespace(
-            call_id,
-            SEARCH_CALENDAR_NAMESPACE,
-            SEARCH_CALENDAR_CREATE_TOOL,
-            &calendar_args,
-        ),
+        calendar_call,
         ev_completed("resp-1"),
     ]));
     if strict_auto_review {
@@ -351,6 +354,10 @@ async fn approved_mcp_tool_call_metadata_records_prior_user_input_request(
         apps_tool_call.pointer("/params/_meta/callId"),
         Some(&json!(call_id))
     );
+    assert_eq!(
+        apps_tool_call.pointer("/params/_meta/itemId"),
+        Some(&json!(originating_item_id))
+    );
     assert_eq!(
         apps_tool_call
             .pointer("/params/_meta/x-codex-turn-metadata/user_input_requested_during_turn"),