feat(syndesis): multi-room clock sync protocol #147
Description
From Phase 03 PLAN.md, REQ-03.
Multi-room synchronization for coordinated playback:
- Clock coordination protocol (Snapcast-style approach per Research R4)
- Zone grouping: assign renderers to zones, sync within zone
- Target: <=5ms offset on wired LAN
- NTP-style round-trip measurement vs PTP-style (open question from plan)
Success criterion: multi-room sync achieves <=5ms offset on wired LAN.