Add SDKMessage local interface for message type safety
Replace any lambda params and message casts with SDKMessage
Remove eslint-disable comments for no-explicit-any
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
- Extract getMessageDir to message-dir.ts
- Extract executeBackground to background-executor.ts
- Extract session creation logic to session-creator.ts
- Extract polling logic to completion-poller.ts
- Extract message processing to message-processor.ts
- Create sync-executor.ts to orchestrate sync execution
- Add ToolContextWithMetadata type to types.ts
- tools.ts now <200 LOC and focused on tool definition
YeonGyu-Kim