[apps] Add is_enabled to app info. (#11417)

- [x] Add is_enabled to app info and the response of `app/list`.
- [x] Update TUI to have Enable/Disable button on the app detail page.

codex-rs/app-server-protocol/schema/json/ServerNotification.json

@@ -193,6 +193,11 @@
           "default": false,
           "type": "boolean"
         },
+        "isEnabled": {
+          "default": true,
+          "description": "Whether this app is enabled in config.toml. Example: ```toml [apps.bad_app] enabled = false ```",
+          "type": "boolean"
+        },
         "logoUrl": {
           "type": [
             "string",