docs: cleanup CLAUDE.md — trim verbosity and consolidate sections

- REST API: collapse 42 endpoint bullets to 7 groupings (42→9L)
- XState: consolidate server/client machines into terse descriptions (21→4L)
- WebSocket: shrink verbose wire format docs (29→2L)
- Message Flow: compress step-by-step narrative (15→1L)
- Tool Detection: tighten framework paths explanation (21→6L)
- Voice Models: merge download sources and UI behavior (4+4+5→1L)
- Codex OAuth: remove implementation details (21→2L)
- Performance: merge with Debug API section (8→3L)

Result: 499 lines → 368 lines (-26% verbosity, all key patterns preserved)

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

Author: lanmower