feat(app-server): add optional thread_id to experimentalFeature/list (#23335)

## Why

`experimentalFeature/list` reports effective feature enablement, but
currently does not resolve it against a working directory where
project-local config.toml files can exist and toggle on/off features
when merged into the effective config after resolving the various config
layers. That means we effectively (and incorrectly) ignore features set
in project-local config.

To address that, this PR exposes an optional `thread_id` param which
allows us to load the thread's `cwd.

## Testing

- `cargo test -p codex-app-server-protocol`
- `cargo test -p codex-app-server experimental_feature_list`

codex-rs/app-server/src/request_processors/catalog_processor.rs

@@ -285,8 +285,28 @@ impl CatalogRequestProcessor {
         &self,
         params: ExperimentalFeatureListParams,
     ) -> Result<ExperimentalFeatureListResponse, JSONRPCErrorError> {
-        let ExperimentalFeatureListParams { cursor, limit } = params;
-        let config = self.load_latest_config(/*fallback_cwd*/ None).await?;
+        let ExperimentalFeatureListParams {
+            cursor,
+            limit,
+            thread_id,
+        } = params;
+        let config = match thread_id.as_deref() {
+            Some(thread_id) => {
+                let thread_id = ThreadId::from_string(thread_id)
+                    .map_err(|err| invalid_request(format!("invalid thread id: {err}")))?;
+                let thread = self
+                    .thread_manager
+                    .get_thread(thread_id)
+                    .await
+                    .map_err(|_| invalid_request(format!("thread not found: {thread_id}")))?;
+                let thread_config = thread.config().await;
+                self.config_manager
+                    .load_latest_config_for_thread(thread_config.as_ref())
+                    .await
+                    .map_err(|err| internal_error(format!("failed to reload config: {err}")))?
+            }
+            None => self.load_latest_config(/*fallback_cwd*/ None).await?,
+        };
         let auth = self.auth_manager.auth().await;
         let workspace_codex_plugins_enabled = self
             .workspace_codex_plugins_enabled(&config, auth.as_ref())