🤖 fix: reduce ProjectSidebar re-renders during streaming

[ammar-agent]

Problem

ProjectSidebar was re-rendering on every streaming delta when watching a chat in another workspace, causing unnecessary CPU usage and UI churn.

Solution

Stabilize unreadStatus Map identity:

• Modified useUnreadTracking to only return a new Map reference when unread boolean values actually change
• Prevents ProjectSidebar re-renders during streaming when unread state is stable
• Uses ref-based deep comparison to maintain Map identity across renders

Code changes:

// Before: New Map created on every workspaceStates or lastReadMap change
const unreadStatus = useMemo(() => {
  const map = new Map<string, boolean>();
  // ... calculate unread status
  return map; // New identity every time
}, [workspaceStates, lastReadMap]);

// After: Map identity preserved when values unchanged
const unreadStatus = useMemo(() => {
  const next = new Map<string, boolean>();
  // ... calculate unread status
  
  // Compare with previous - only return new Map if values changed
  const prev = unreadStatusRef.current;
  if (prev.size === next.size) {
    let same = true;
    for (const [k, v] of next) {
      if (prev.get(k) !== v) {
        same = false;
        break;
      }
    }
    if (same) return prev; // Maintain identity
  }
  
  unreadStatusRef.current = next;
  return next;
}, [workspaceStates, lastReadMap]);

Testing

Manual verification:

• ✅ Streaming in workspace A while viewing workspace B no longer causes sidebar re-renders
• ✅ Unread status updates correctly on workspace switches and stream completion
• ✅ Toggle unread function works correctly
• ✅ Drag-and-drop project reordering remains smooth

Impact

Fixed:

• ProjectSidebar no longer re-renders on every streaming delta in non-selected workspaces
• Reduced unnecessary CPU usage during streaming operations

Not fixed (separate issue):

• ProjectSidebar still re-renders every 3 seconds due to useGitStatus() call at line 611
• Will be addressed in a follow-up PR by removing the direct hook call and passing git status as a prop

Notes

The comparison logic handles all edge cases correctly:

• Empty maps
• Size changes (added/removed workspaces)
• Key changes (different workspace IDs)
• Value changes (unread status flips)

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