Synthesized audio system with 9 distinct SFX (click, success, warning,
danger, purchase, achievement, era transition, info) mapped to all game
notifications, plus generative ambient background music with chord
progressions. Adds SFX volume slider to settings alongside existing
music volume control. No audio files or npm dependencies needed.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
