Add slim test suite for manus & Ralph features

[OniReimu]

Summary

Implemented comprehensive end-to-end test suite for superpowers-ng features:

• 2 unit tests for manus pretool hook and Ralph status block parsing
• 3 integration tests for Ralph status emission, manus+Ralph combined workflow, and manus session resume
• Helper functions for JSON validation, status block extraction, and file assertions
• Complete documentation in README with test descriptions and usage

Total runtime: ~6-9 minutes (within 10-15 minute target).

Test Coverage

✓ Manus-styled planning with session persistence
✓ Ralph loop integration with status blocks
✓ Hook system and .active marker behavior
✓ EXIT_SIGNAL logic with active planning