feat(32-02): add prevCategoriesRef to track dispatched values

- Add useRef to track previous category values
- Prevents circular updates by using ref instead of selectors
- Stores last dispatched values for comparison

jam-ui/src/hooks/useMixerHelper.js

@@ -78,6 +78,15 @@ const useMixerHelper = () => {
   const previousMyTracksRef = useRef([]);
   const previousMixerIdsRef = useRef(null);
 
+  // Track previous category values for comparison
+  const prevCategoriesRef = useRef({
+    metronome: [],
+    backing: [],
+    jam: [],
+    recording: [],
+    adhoc: []
+  });
+
   // Composed selectors with shallowEqual - reduces 21 subscriptions to 6
   const coreMixers = useSelector(selectCoreMixerState, shallowEqual);
   const trackMixers = useSelector(selectTrackMixerState, shallowEqual);