- Add drag threshold and layout frame stride to splitter drag utility
- Use onPreview callback to animate splitter offset via translate3d during drag
- Simplify resize class and cleanup logic in missing browser methods
- Replace deferred release UI cleanup with direct activation/cleanup calls
- Update CSS to add resizing overlay and remove transition during resize
- Add test covering compositor preview behavior and CSS constraints
Replace duplicated inline drag handlers in queue_methods.js and
missing_browser_methods.js with a new startSplitterDrag() helper in
web/resolver/utils/splitter_drag.js.
The utility centralizes pointer/mouse event binding, RAF throttling,
and touch-cancellation cleanup, cutting net code across the two
callers while preserving existing behaviour (bounds, edge-open
threshold, collapse preview, and settle/cleanup timing).
Dariusz L