Feishu API rejects messages with content exceeding ~64KB with error
230001 "invalid message content". Added truncation at 60,000 characters
to prevent this, with a notice appended to truncated content.
- Added ContentBlock enum for multimodal content representation (text, image).
- Enhanced ChatMessage struct to include media references.
- Updated InboundMessage and OutboundMessage to use MediaItem for media handling.
- Implemented media download and upload functionality in FeishuChannel.
- Modified message processing in the gateway to handle media items.
- Improved logging for message processing and media handling in debug mode.
- Refactored message serialization for LLM providers to support content blocks.
- Removed internal history management from AgentLoop.
- Updated process method to accept conversation history as a parameter.
- Adjusted continue_with_tool_results to work with external history.
- Added OutboundDispatcher for handling outbound messages from MessageBus.
- Introduced InboundMessage and OutboundMessage structs for message handling.
- Updated Channel trait to include message handling and publishing to MessageBus.
- Refactored Session to manage chat histories instead of AgentLoop instances.
- Enhanced GatewayState to start message processing loops for inbound and outbound messages.
