Update Phase 22 to capture full synthesis engine implementation

This branch pulled forward and implemented most of Phase 25:
- Sampled piano with multi-sampling (C2-C5)
- Tone.js integration (FM, AM, Membrane, Metal, Pluck, Duo)
- Advanced dual-oscillator synth (863 lines)
- Effects chain (reverb, delay, chorus, distortion)
- XY Pad / macro controls (370 lines)
- Lazy audio loading
- 5,963 lines of audio tests
- 1,808-line synthesis spec

Also includes memory leak fixes, code deduplication, and
architecture audit from original scope.

Renumbered phases 23-33 to account for new Phase 22.
Marked Phase 25 as substantially complete.

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: adewale