v0.0.5

refactor: simplify variation system to preserve groove

Simplified generateVariation() to only toggle single hits rather than complex track copying, sliding, and swapping operations that often destroyed the groove character. Now each variation press:
- Picks a random track (kick, snare, or ghost)
- Finds a hit position from the base pattern
- Toggles that hit on/off in the current pattern

This creates subtle variations while maintaining the core rhythm. Also removed unused generateVariationWithSeed() function and getTrackFromPattern() helper.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>