- Add ChannelCapability.PROCESSING_STATUS and capability detection for supported channels
- Implement mark_message_processing_started/finished in Telegram, Slack, Discord, Feishu modules
- Telegram: manage typing lifecycle with max duration and explicit stop
- Slack: add/remove reaction as processing indicator
- Discord: start/stop typing indicator with async task management
- Feishu: add/remove reaction for processing status
- Refactor message chain to invoke processing status hooks for supported channels
- Ensure processing status is properly finished on sync and async message handling paths
- Add tests for processing status lifecycle and capability detection across channels
- Update stop_streaming logic to await inflight initial flush task, preventing duplicate message sends on stream stop
- Change message edit/delete methods to return Optional[bool] for clearer channel mismatch handling
- Refine Feishu logging to include message_id instead of full data object
- Suppress allowed_objects warnings in __init__.py
- Add test to verify stop_streaming waits for inflight flush before final edit
- Update .pylintrc to use 'E' for error enabling
