feat: move operation hints to persistent bottom left controls

app/src/components/BottomLeftControls.tsx

@@ -109,12 +109,14 @@ export function BottomLeftControls() {
               onClick={() => setObjectRenderMode(mode)}
               active={objectRenderMode === mode}
               className={modeBtn(objectRenderMode === mode)}
-            >
-              <Icon size={17} weight={objectRenderMode === mode ? 'fill' : 'regular'} />
             </AppButton>
           </ControlTooltip>
         ))}
       </div>
+
+      <div className={`${chrome.bar} hidden md:flex h-10 items-center px-3 text-white/50 text-xs tracking-wide`}>
+        💡 Left-click rotate, Right-click pan, Scroll zoom
+      </div>
     </div>
   )
 }

app/src/components/WorldViewer.tsx

@@ -31,7 +31,6 @@ function ModelLoader() {
         <div className="text-white text-base font-semibold tracking-wide drop-shadow-md">Downloading Model...</div>
         <div className="text-white/70 text-xs mt-2 max-w-xs text-center space-y-1">
           <p>This may take a moment depending on model size and network speed.</p>
-          <p className="mt-2 text-white/50">💡 Hint: Left-click to rotate, Right-click to pan, Scroll to zoom.</p>
         </div>
       </div>
     </Html>