GauntletHUD in UILayer shows TIMER: MM:SS (PB: MM:SS). Timer starts on
room entry, resets on room change, records personal bests to
user://gauntlet-stats.json. Session summary printed on disconnect.
Hidden in non-gauntlet mode (anti-tedium guard).
Adds room_id and gauntlet_mode fields to GameState, parsed from
ObserverSnapshot. Main.gd wires update_from_state() and finalize().
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
