- Updated `LegacyContext.send_message` to handle rich message chains using `send_chain`.
- Introduced `LegacyStar` class for backward compatibility with legacy plugins.
- Added `register` decorator for legacy plugin metadata.
- Enhanced `MessageChain` class with `to_payload` and `is_plain_text_only` methods.
- Updated `AstrMessageEvent.send` method to utilize `send_chain` for rich messages.
- Implemented `send_chain` method in `PlatformClient` for sending complex message structures.
- Added capability routing for `platform.send_chain`.
- Introduced tests for new functionality, ensuring compatibility with legacy plugins and message handling.
- Added Peer class for managing peer-to-peer communication, including initialization, invocation, and cancellation of requests.
- Introduced Transport abstract base class with StdioTransport and WebSocketTransport implementations for message handling.
- Created Star class for error handling in event-driven architecture.
- Developed MemoryTransport for testing purposes, allowing in-memory communication between peers.
- Implemented unit tests for Peer functionality, protocol message parsing, and runtime integration with plugins.
- Established entry point tests to ensure package import and command-line interface functionality.
