…ness

Fix 5 critical issues in modal resize functionality:

1. Viewport-aware bounds management
   - Add window resize listener to recompute effectiveMinSize
   - Dialog stays within viewport when browser window resizes
   - Prevents modal from getting stuck off-screen

2. Proper max-size clamping
   - Respect true maxWidth/maxHeight with 16px margin
   - Shift or shrink dialog when near viewport edges
   - No longer forces dialog outside viewport

3. Robust resize state management
   - Add mouseleave and blur listeners to stop resize
   - Check event.buttons === 0 in handleResize
   - Resize reliably stops even if mouseup is lost

4. Smooth performance with RAF batching
   - Batch cell-size and scrollbar updates into single RAF callback
   - Eliminate multiple synchronous layout passes
   - No more jank during fast resize

5. Remove duplicate side-effects
   - Gate ResizeObserver callback while resizeState is active
   - Prevent double RAF scheduling
   - Cleaner control flow

All 109 tests passing.

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Co-Authored-By: Claude <noreply@anthropic.com>