fix(29): revise plan based on checker feedback

- Split Task 1 into Task 1a (stabilize useMixerHelper) and Task 1b (memoize MixersContext)
- Add useMixerHelper.js to files_modified
- Add getMixer useCallback wrapping as prerequisite for context memoization
- Add key_link verifying useMixerHelper -> MixersContext wiring
- Add CTX-00 success criterion for getMixer stabilization

Issues addressed:
- task_completeness: Task 1 now includes getMixer useCallback wrapping
- key_links_planned: Added verification for useMixerHelper stabilization

.planning/phases/29-context-optimization/29-01-PLAN.md

@@ -5,6 +5,7 @@ type: execute
 wave: 1
 depends_on: []
 files_modified:
+  - jam-ui/src/hooks/useMixerHelper.js
   - jam-ui/src/context/MixersContext.js
   - jam-ui/src/context/VuContext.js
   - jam-ui/src/context/GlobalContext.js
@@ -22,7 +23,11 @@ must_haves:
     - "VU update does not re-render volume sliders"
     - "MixersContext.Provider value is memoized"
     - "Context consumers only re-render when their specific data changes"
+    - "useMixerHelper returns stable function references"
   artifacts:
+    - path: "jam-ui/src/hooks/useMixerHelper.js"
+      provides: "Stable function references via useCallback"
+      contains: "useCallback"
     - path: "jam-ui/src/context/MixersContext.js"
       provides: "Memoized context provider value"
       contains: "useMemo"
@@ -36,6 +41,10 @@ must_haves:
       provides: "Memoized context consumer"
       contains: "memo"
   key_links:
+    - from: "useMixerHelper.js"
+      to: "MixersContext.js"
+      via: "stable getMixer function"
+      pattern: "const getMixer = useCallback"
     - from: "MixersContext.Provider"
       to: "useMixerHelper"
       via: "useMemo wrapper"
@@ -69,13 +78,70 @@ Output: Memoized context providers (MixersContext, VuContext, GlobalContext) and
 <tasks>
 
 <task type="auto">
-  <name>Task 1: Memoize MixersContext provider value</name>
+  <name>Task 1a: Stabilize useMixerHelper function references</name>
+  <files>
+    jam-ui/src/hooks/useMixerHelper.js
+  </files>
+  <action>
+Wrap internal functions in useMixerHelper.js with useCallback to ensure stable references. Without this, memoizing MixersContext.Provider value is ineffective because the mixerHelper object changes every render.
+
+**CRITICAL: The `getMixer` function (line 128) is NOT wrapped with useCallback. This causes ALL dependent functions to recreate every render.**
+
+1. Wrap `getMixer` with useCallback:
+   ```javascript
+   const getMixer = useCallback((mixerId, mode) => {
+     // Only default to mixMode if mode is undefined, not if it's explicitly false
+     if (mode === undefined) {
+       mode = mixMode;
+     }
+     return allMixersRef.current[(mode ? 'M' : 'P') + mixerId];
+   }, [mixMode]);
+   ```
+   Note: Uses `allMixersRef.current` (ref, not dependency) and `mixMode` (selector value).
+
+2. Verify these functions are already wrapped (they should be - just confirm):
+   - `fillTrackVolumeObject` (line 136) - uses useCallback, depends on getMixer
+   - `setMixerVolume` (line 176) - uses useCallback
+   - `mediaMixers` (line 216) - uses useCallback
+   - `updateMixerData` (line 235) - uses useCallback
+   - `getMixerByTrackId` (line 353) - uses useCallback
+   - `groupedMixersForClientId` (line 369) - uses useCallback
+   - `findMixerForTrack` (line 397) - uses useCallback
+   - `mixersForGroupId` (line 592) - uses useCallback
+   - `getGroupMixer` (line 608) - uses useCallback
+   - `getMixerByResourceId` (line 705) - uses useCallback
+   - `mute` (line 721) - uses useCallback, depends on getMixer
+   - `faderChanged` (line 751) - uses useCallback, depends on getMixer
+   - `panChanged` (line 811) - uses useCallback, depends on getMixer
+   - `loopChanged` (line 835) - uses useCallback, depends on getMixer
+   - `updateVU` (line 896) - uses useCallback, depends on getMixer
+   - `refreshMixer` (line 928) - uses useCallback, depends on getMixer
+
+3. After wrapping getMixer, these dependent functions will automatically stabilize because their `getMixer` dependency will now be stable.
+
+**Why this matters:** Without stable `getMixer`, the dependency chain causes 10+ functions to recreate every render, defeating context memoization.
+  </action>
+  <verify>
+1. Run `grep -n "const getMixer = useCallback" jam-ui/src/hooks/useMixerHelper.js` - should find the wrapped function
+2. Run `cd /Users/nuwan/Code/jam-cloud/jam-ui && npm run build` - should compile without errors
+  </verify>
+  <done>
+- getMixer is wrapped with useCallback
+- All dependent functions now have stable references
+- Build passes without errors
+  </done>
+</task>
+
+<task type="auto">
+  <name>Task 1b: Memoize MixersContext provider value</name>
   <files>
     jam-ui/src/context/MixersContext.js
   </files>
   <action>
 Memoize the MixersContext.Provider value to prevent new object creation on every render.
 
+**PREREQUISITE:** Task 1a must be complete - useMixerHelper must return stable references for this memoization to be effective.
+
 1. Import `useMemo` from 'react'
 2. Wrap the `mixerHelper` value with `useMemo`:
    ```javascript
@@ -83,9 +149,7 @@ Memoize the MixersContext.Provider value to prevent new object creation on every
    ```
 3. Pass `value` to `MixersContext.Provider` instead of `mixerHelper` directly
 
-The useMixerHelper hook already returns stable references (verified: all functions use useCallback, myTracks uses useMemo). The memoization ensures the context value object itself doesn't recreate unless mixerHelper changes.
-
-Do NOT change useMixerHelper.js - the returned object from useMixerHelper already has stable function references via useCallback (faderChanged, findMixerForTrack, updateMixerData, etc.) and memoized values (myTracks via useMemo).
+Now that useMixerHelper returns stable function references (after Task 1a), the memoized context value will only change when actual data changes (allMixers, mixMode, etc.), not on every render.
   </action>
   <verify>
 1. Run `cd /Users/nuwan/Code/jam-cloud/jam-ui && npm run build` - should compile without errors
@@ -222,6 +286,9 @@ After all tasks complete:
 
 2. **Code verification:**
    ```bash
+   # Check useMixerHelper getMixer stabilization
+   grep -n "const getMixer = useCallback" jam-ui/src/hooks/useMixerHelper.js
+
    # Check MixersContext memoization
    grep -n "useMemo" jam-ui/src/context/MixersContext.js
 
@@ -243,6 +310,7 @@ After all tasks complete:
 </verification>
 
 <success_criteria>
+- CTX-00: useMixerHelper.getMixer is wrapped with useCallback (prerequisite for CTX-01)
 - CTX-01: MixersContext.Provider value is memoized (useMemo wraps mixerHelper)
 - CTX-02: VuContext separated from MixerConfigContext (already done in Phase 28, now memoized)
 - CTX-03: Context consumers only subscribe to data they actually use (React.memo prevents prop-unchanged re-renders)