Introduce the new channel unification architecture:
- Core framework: base channel class, bus, consumer, channel manager,
middleware, mixins, capabilities, formatter, retry, plugin system
- Telegram channel implementation with bot token validation
- Discord channel implementation with bot token validation
- Refactored iMessage to use new base channel architecture
- Updated CLI: /channel commands, serve mode, channel setup wizard
- Updated onboard wizard to support multi-channel selection
- Config settings for all channel types
- Stream events: media attachment support, done event content field
- Comprehensive test coverage for channels, bus, and manager
dinos