Add comprehensive tests for context compaction functionality:
- Request summary from agent of completed work
- Replace conversation history with summary
- Measure context reduction achieved
- Integration with ContextMonitor
Tests cover:
- Summary generation and prompt validation
- Conversation history replacement
- Context reduction metrics (target: 40-50%)
- Error handling and failure cases
- Integration with context monitoring
Coverage: 100% for context_compaction module
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>