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/main.js

@@ -83,6 +83,10 @@ generator.onPlacementUpdate = (preview) => {
     }
 };
 
+generator.onDoorBlocked = (exitData) => {
+    renderer.blockDoor(exitData);
+};
+
 // 6. Handle Clicks
 const handleClick = (x, y, doorMesh) => {
     // PRIORITY 1: Tile Placement Mode - ignore all clicks
@@ -92,26 +96,33 @@ const handleClick = (x, y, doorMesh) => {
     }
 
     // PRIORITY 2: Door Click (must be adjacent to player)
-    if (doorMesh && doorMesh.userData.isDoor && !doorMesh.userData.isOpen) {
-        const doorExit = doorMesh.userData.cells[0];
-
-        if (game.isPlayerAdjacentToDoor(doorExit)) {
-
-
-            // Open door visually
-            renderer.openDoor(doorMesh);
-
-            // Get proper exit data with direction
-            const exitData = doorMesh.userData.exitData;
-            if (exitData) {
-                generator.selectDoor(exitData);
-            } else {
-                console.error('[Main] Door missing exitData');
-            }
-        } else {
-
+    if (doorMesh && doorMesh.userData.isDoor) {
+        if (doorMesh.userData.isBlocked) {
+            ui.showModal('¡Derrumbe!', 'Esta puerta está bloqueada por un derrumbe. No se puede pasar.');
+            return;
+        }
+
+        if (!doorMesh.userData.isOpen) {
+            const doorExit = doorMesh.userData.cells[0];
+
+            if (game.isPlayerAdjacentToDoor(doorMesh.userData.cells)) {
+
+
+                // Open door visually
+                renderer.openDoor(doorMesh);
+
+                // Get proper exit data with direction
+                const exitData = doorMesh.userData.exitData;
+                if (exitData) {
+                    generator.selectDoor(exitData);
+                } else {
+                    console.error('[Main] Door missing exitData');
+                }
+            } else {
+                // Optional: Message if too far?
+            }
+            return;
         }
-        return;
     }
 
     // PRIORITY 3: Normal cell click (player selection/movement)