feat(simulation): add Zone Gate gauntlet room and zone crossing detection (#512)

New test_world room with two zones (Terminal/Corridor) separated by
a door. Adds ZoneCrossEventQueue resource and detect_zone_crossings
system to fire events when the player crosses zone boundaries.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/test_world/rooms/mod.rs

@@ -17,3 +17,4 @@ pub mod pause_chamber;
 pub mod shift_change;
 pub mod sound_lab;
 pub mod sprint_gauntlet;
+pub mod zone_gate;