Add setTimeout support to code mode (#16153)

The implementation is less than ideal - it starts a thread per timer. A
better approach might be to switch to tokio and use their timer
imlementation.

codex-rs/code-mode/src/description.rs

@@ -26,6 +26,8 @@ const EXEC_DESCRIPTION_TEMPLATE: &str = r#"Run JavaScript code to orchestrate/co
 - `store(key: string, value: any)`: stores a serializable value under a string key for later `exec` calls in the same session.
 - `load(key: string)`: returns the stored value for a string key, or `undefined` if it is missing.
 - `notify(value: string | number | boolean | undefined | null)`: immediately injects an extra `custom_tool_call_output` for the current `exec` call. Values are stringified like `text(...)`.
+- `setTimeout(callback: () => void, delayMs?: number)`: schedules a callback to run later and returns a timeout id. Pending timeouts do not keep `exec` alive by themselves; await an explicit promise if you need to wait for one.
+- `clearTimeout(timeoutId?: number)`: cancels a timeout created by `setTimeout`.
 - `ALL_TOOLS`: metadata for the enabled nested tools as `{ name, description }` entries.
 - `yield_control()`: yields the accumulated output to the model immediately while the script keeps running."#;
 const WAIT_DESCRIPTION_TEMPLATE: &str = r#"- Use `wait` only after `exec` returns `Script running with cell ID ...`.
@@ -556,4 +558,11 @@ mod tests {
         );
         assert!(description.contains("### `foo` (`foo`)"));
     }
+
+    #[test]
+    fn exec_description_mentions_timeout_helpers() {
+        let description = build_exec_tool_description(&[], /*code_mode_only*/ false);
+        assert!(description.contains("`setTimeout(callback: () => void, delayMs?: number)`"));
+        assert!(description.contains("`clearTimeout(timeoutId?: number)`"));
+    }
 }