[apps] Store apps tool cache in disk to reduce startup time. (#11822)

We now write MCP tools from installed apps to disk cache so that they
can be picked up instantly at startup. We still do a fresh fetch from
remote MCP server but it's non blocking unless there's a cache miss.

- [x] Store apps tool cache in disk to reduce startup time.

codex-rs/tui/src/chatwidget/tests.rs

@@ -1627,6 +1627,7 @@ async fn make_chatwidget_manual(
         mcp_startup_status: None,
         connectors_cache: ConnectorsCacheState::default(),
         connectors_prefetch_in_flight: false,
+        connectors_force_refetch_pending: false,
         interrupts: InterruptManager::new(),
         reasoning_buffer: String::new(),
         full_reasoning_buffer: String::new(),
@@ -4582,6 +4583,42 @@ async fn apps_refresh_failure_keeps_existing_full_snapshot() {
     );
 }
 
+#[tokio::test]
+async fn apps_refresh_failure_with_cached_snapshot_triggers_pending_force_refetch() {
+    let (mut chat, _rx, _op_rx) = make_chatwidget_manual(None).await;
+    chat.config.features.enable(Feature::Apps);
+    chat.bottom_pane.set_connectors_enabled(true);
+    chat.connectors_prefetch_in_flight = true;
+    chat.connectors_force_refetch_pending = true;
+
+    let full_connectors = vec![codex_chatgpt::connectors::AppInfo {
+        id: "unit_test_apps_refresh_failure_pending_connector".to_string(),
+        name: "Notion".to_string(),
+        description: Some("Workspace docs".to_string()),
+        logo_url: None,
+        logo_url_dark: None,
+        distribution_channel: None,
+        branding: None,
+        app_metadata: None,
+        labels: None,
+        install_url: Some("https://example.test/notion".to_string()),
+        is_accessible: true,
+        is_enabled: true,
+    }];
+    chat.connectors_cache = ConnectorsCacheState::Ready(ConnectorsSnapshot {
+        connectors: full_connectors.clone(),
+    });
+
+    chat.on_connectors_loaded(Err("failed to load apps".to_string()), true);
+
+    assert!(chat.connectors_prefetch_in_flight);
+    assert!(!chat.connectors_force_refetch_pending);
+    assert_matches!(
+        &chat.connectors_cache,
+        ConnectorsCacheState::Ready(snapshot) if snapshot.connectors == full_connectors
+    );
+}
+
 #[tokio::test]
 async fn apps_partial_refresh_uses_same_filtering_as_full_refresh() {
     let (mut chat, _rx, _op_rx) = make_chatwidget_manual(None).await;