feat(gauntlet): replace Cleanser with Ghost powerup sticky bypass (v2.4.2)

- Remove entire Cleanser system (signal, vars, HUD, input, RPCs, bot AI)
- Ghost (Invisible Mode) now bypasses sticky tiles in Gauntlet
- Grant Ghost powerup every 2 missions instead of Cleanser charges
- Ghost tiles spawn naturally on Gauntlet arena (15% chance)
- Bots use Ghost powerup when boxed in by sticky tiles
- Players pushed into sticky while Ghost are not slowed
- Remove use_cleanser input action from project.godot
- Remove CleanserHBox UI from gauntlet_hud.tscn
- Bump version to 2.4.2

scripts/managers/special_tiles_manager.gd

@@ -547,9 +547,11 @@ func spawn_powerups_around(center: Vector2i, force_powerups: bool = true, only_c
 					# Spawn ONLY common tiles (7-10) in Stop n Go mode (User Request)
 					item_id = rng.randi_range(7, 10)
 				elif LobbyManager.is_game_mode(GameMode.Mode.GAUNTLET):
-					# Gauntlet mode: No power-up tile spawns from world.
-					# Only common tiles (7-10) spawn; Smack/Cleanser are handled separately.
-					item_id = rng.randi_range(7, 10)
+					# Gauntlet mode: mostly common tiles, but ghost (14) can spawn too.
+					if rng.randf() < 0.85:
+						item_id = rng.randi_range(7, 10)
+					else:
+						item_id = 14 # Ghost powerup only
 				else:
 					# Other modes: 80% Chance for Common Tile (7-10), 20% for PowerUp
 					if rng.randf() < 0.8: