feat: Ensure stone layer chunks always render and remain visible

js/main.js

@@ -78,6 +78,15 @@ function simulationLoop(timestamp) {
     // Update physics with timestamp for rate limiting
     updatePhysics(timestamp);
     
+    // Force stone layer chunks to be rendered every frame
+    const visibleChunks = getVisibleChunks();
+    for (const { chunkX, chunkY, isVisible } of visibleChunks) {
+        if (isVisible && chunkY === 1) {
+            // Mark stone layer chunks as dirty to ensure they're always rendered
+            dirtyChunks.add(getChunkKey(chunkX, chunkY));
+        }
+    }
+    
     // Render
     render();