fix: hardcode NPC zone coordinates to strictly prevent tiles spawning underneath candy cannon

scripts/managers/gauntlet_manager.gd

@@ -412,12 +412,10 @@ func _apply_arena_setup() -> void:
 			var pos = Vector2i(x, z)
 			
 			# Center 3x3 block: NPC obstacle (Candy Pump)
-			if _is_npc_zone(pos):
-				# Make the floor empty (-1) beneath the Candy Pump
-				# We need to clear all possible layers just in case
-				gridmap.set_cell_item(Vector3i(x, 0, z), -1)
-				gridmap.set_cell_item(Vector3i(x, 1, z), -1)
-				gridmap.set_cell_item(Vector3i(x, 2, z), -1)
+			if x >= 8 and x <= 10 and z >= 8 and z <= 10:
+				# Hardcode clear all possible layers beneath the Candy Pump
+				for layer in range(5):
+					gridmap.set_cell_item(Vector3i(x, layer, z), -1)
 				continue
 			
 			# Boundary walls: perimeter (row 0, row 19, col 0, col 19)
@@ -451,10 +449,7 @@ func _apply_arena_setup() -> void:
 
 func _is_npc_zone(pos: Vector2i) -> bool:
 	"""Check if a position is within the center 3x3 NPC zone."""
-	var half = NPC_SIZE / 2 # integer division = 1
-	var min_coord = NPC_CENTER - Vector2i(half, half) # (8, 8)
-	var max_coord = NPC_CENTER + Vector2i(half, half) # (10, 10)
-	return pos.x >= min_coord.x and pos.x <= max_coord.x and pos.y >= min_coord.y and pos.y <= max_coord.y
+	return pos.x >= 8 and pos.x <= 10 and pos.y >= 8 and pos.y <= 10
 
 func get_spawn_points(player_count: int) -> Array[Vector2i]:
 	"""Return spawn positions based on player count. Inside boundary walls."""
@@ -514,7 +509,7 @@ func _spawn_mission_tiles() -> void:
 				var pos = Vector2i(x, z)
 				
 				# Skip NPC pump zone (center 3x3)
-			if _is_npc_zone(pos):
+				if x >= 8 and x <= 10 and z >= 8 and z <= 10:
 					continue
 				
 				# Check base floor — don't spawn on void (or walls if they were still obstacles)
@@ -858,6 +853,8 @@ func sync_growth_telegraph(cells: Array) -> void:
 
 	for cell in cells:
 		var pos = cell as Vector2i
+		if pos.x >= 8 and pos.x <= 10 and pos.y >= 8 and pos.y <= 10: continue
+		
 		# Telegraph overlay tile on Layer 2 (still passable).
 		gridmap.set_cell_item(Vector3i(pos.x, 2, pos.y), TILE_TELEGRAPH)
 		_spawn_telegraph_highlight(pos)
@@ -929,6 +926,8 @@ func sync_growth_apply(cells: Array) -> void:
 	if not gridmap: return
 	for cell in cells:
 		var pos = cell as Vector2i
+		if pos.x >= 8 and pos.x <= 10 and pos.y >= 8 and pos.y <= 10: continue
+		
 		gridmap.set_cell_item(Vector3i(pos.x, 2, pos.y), TILE_STICKY)
 		sticky_cells[pos] = true
 
@@ -1518,6 +1517,8 @@ func sync_bubble_spawn(center: Vector2i, cells: Array) -> void:
 	# Telegraph-style warning overlay on the footprint (still passable).
 	for c in cells:
 		var pos = c as Vector2i
+		if pos.x >= 8 and pos.x <= 10 and pos.y >= 8 and pos.y <= 10: continue
+		
 		gridmap.set_cell_item(Vector3i(pos.x, 2, pos.y), TILE_TELEGRAPH)
 	_spawn_bubble_visual(center)
 	if SfxManager:
@@ -1539,6 +1540,8 @@ func sync_bubble_explode(center: Vector2i, cells: Array) -> void:
 		return
 	for c in cells:
 		var pos = c as Vector2i
+		if pos.x >= 8 and pos.x <= 10 and pos.y >= 8 and pos.y <= 10: continue
+		
 		gridmap.set_cell_item(Vector3i(pos.x, 2, pos.y), TILE_STICKY)
 		sticky_cells[pos] = true
 	# Medium shake — bubbles hit harder than a normal growth tick.