Track parent turns for nested Codex requests (#35835)

## What changed

- Propagate the initiating turn ID through agent spawns, follow-up tasks, reviews, and delegated Codex sessions.
- Add `parent_turn_id` to Responses client and turn metadata while keeping it out of external MCP metadata.
- Preserve parent-turn provenance across queued agent messages when their triggering parent is unambiguous.

## Testing

- Cover spawned, resumed, nested, reviewed, delegated, and WebSocket request metadata.
- Verify queued messages do not claim ambiguous or queue-only parent turns.

GitOrigin-RevId: 481fdebbe7df2031880fe259509273cce50b20a8

codex-rs/mcp-server/src/codex_tool_runner.rs

@@ -119,6 +119,7 @@ pub async fn run_codex_tool_session(
         },
         client_user_message_id: None,
         trace: None,
+        parent_turn_id: None,
     };
 
     if let Err(e) = thread.submit_with_id(submission).await {

codex-rs/mcp-server/src/message_processor.rs

@@ -560,6 +560,7 @@ impl MessageProcessor {
                 op: codex_protocol::protocol::Op::Interrupt,
                 client_user_message_id: None,
                 trace: None,
+                parent_turn_id: None,
             })
             .await
         {