Remove premature Voice/VoiceConversation from SOUND_EVENT_ASSETS (D-072
defers murmur to end-to-end sprint). Extract current_zone_id in
GameState.apply_snapshot() as first-class field, eliminating O(N) tile
scan in main.gd (D-020 server-authoritative). Add dir.list_dir_end()
after registry scan. Add rapid zone-crossing + _load_prefs() roundtrip
tests. Enhance comments on hub/workplace same-asset pattern, station
base hum, and confrontation dip replacement semantics.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>