Reorganized runCodex.ts to improve maintainability by extracting:
- CodexSession class for session lifecycle management
- CodexLocalLauncher and CodexRemoteLauncher for mode-specific initialization
- CodexEventConverter for MCP message handling and UI buffer updates
- CodexSessionScanner for resume file discovery
- emitReadyIfIdle utility for ready event emission
Added codexSessionId field to metadata schema for session tracking.
Updated UI components to work with refactored architecture.