Fix GPU resource leaks and re-entrant world loading for instance transitions

Reset descriptor pools in CharacterRenderer/M2Renderer/WMORenderer on map
change to prevent VK_ERROR_DEVICE_LOST from pool exhaustion. Defer re-entrant
SMSG_NEW_WORLD during active world load to avoid recursive cleanup crashes.
Gate swim bubbles on swimming state, skip redundant shadow pipeline re-init,
add WOWEE_SKIP_* env vars for render isolation debugging.

src/rendering/wmo_renderer.cpp

@@ -1059,6 +1059,11 @@ void WMORenderer::clearAll() {
             if (entry.texture) entry.texture->destroy(device, allocator);
             if (entry.normalHeightMap) entry.normalHeightMap->destroy(device, allocator);
         }
+
+        // Reset descriptor pool so new allocations succeed after reload
+        if (materialDescPool_) {
+            vkResetDescriptorPool(device, materialDescPool_, 0);
+        }
     }
 
     loadedModels.clear();