Implement tile discarding, blocked doors, and correct corridor exits

- Updated TileDefinitions.js: Added 4-way exits to corridor_straight and corridor_steps (N/S y=3,4; E/W x=3,4).
- Updated DungeonGenerator.js: Added cancelPlacement() logic and onDoorBlocked callback.
- Updated GameRenderer.js: Implemented blockDoor() to visualize blocked passages, and improved isPlayerAdjacentToDoor.
- Updated UIManager.js: Added custom showModal/showConfirm and Discard button for tile placement.
- Updated main.js: Handled blocked door clicks and hooked up UI events.
- Updated GameEngine.js: Improved door adjacency checks.
- Updated CameraManager.js: Preserved camera rotation on centerOn.
- Added door1_blocked.png asset.

src/engine/game/GameEngine.js

@@ -89,14 +89,23 @@ export class GameEngine {
 
     }
 
-    isPlayerAdjacentToDoor(doorExit) {
+    isPlayerAdjacentToDoor(doorCells) {
         if (!this.player) return false;
 
-        const dx = Math.abs(this.player.x - doorExit.x);
-        const dy = Math.abs(this.player.y - doorExit.y);
+        // doorCells should be an array of {x, y} objects
+        // If it sends a single object, wrap it
+        const cells = Array.isArray(doorCells) ? doorCells : [doorCells];
 
-        // Adjacent means distance of 1 in one direction and 0 in the other
-        return (dx === 1 && dy === 0) || (dx === 0 && dy === 1);
+        for (const cell of cells) {
+            const dx = Math.abs(this.player.x - cell.x);
+            const dy = Math.abs(this.player.y - cell.y);
+
+            // Adjacent means distance of 1 in one direction and 0 in the other
+            if ((dx === 1 && dy === 0) || (dx === 0 && dy === 1)) {
+                return true;
+            }
+        }
+        return false;
     }
 
     update(time) {