feat(cli): make /btw command non-blocking with parallel execution

- Add btwItem state management independent from pendingItem
- Add cancelBtw functionality to abort in-flight BTW API calls
- Allow /btw commands to execute concurrently with main responses
- Add isBtwCommand utility function
- Update BtwMessage UI with cleaner styling (remove spinner)
- Add tests for concurrent /btw execution scenarios
- Update layouts to render BTW messages in fixed bottom area

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

packages/cli/src/nonInteractiveCliCommands.ts

@@ -42,6 +42,7 @@ export const ALLOWED_BUILTIN_COMMANDS_NON_INTERACTIVE = [
   'init',
   'summary',
   'compress',
+  'btw',
   'bug',
 ] as const;