Fix: update parallel tool call exec approval to approve on request id (#11162)

### Summary

In parallel tool call, exec command approvals were not approved at
request level but at a turn level. i.e. when a single request is
approved, the system currently treats all requests in turn as approved.

### Before

https://github.com/user-attachments/assets/d50ed129-b3d2-4b2f-97fa-8601eb11f6a8

### After

https://github.com/user-attachments/assets/36528a43-a4aa-4775-9e12-f13287ef19fc

codex-rs/protocol/src/protocol.rs

@@ -198,6 +198,9 @@ pub enum Op {
     ExecApproval {
         /// The id of the submission we are approving
         id: String,
+        /// Turn id associated with the approval event, when available.
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        turn_id: Option<String>,
         /// The user's decision in response to the request.
         decision: ReviewDecision,
     },