perf(scene-graph): accelerate axis-aligned hit tests (#534)
* perf(scene-graph): accelerate axis-aligned hit tests
- Reuse cached world positions for untransformed node chains
- Preserve exact matrix hit testing beneath rotated and flipped ancestors
- Profile pointer, hit-test, cached, overlay, and volatile rendering at 500 and 2,000 nodes
* fix(vue): restore layer drop indicators
- Forward reactive drag instructions through virtualized layer item slots
- Render above, below, and child feedback before the drop completes
- Add browser regressions for reorder lines and container highlights
* fix(scene-graph): harden hit-test performance coverage
- Cache transformed ancestry within each hit-test traversal
- Invalidate absolute positions after preview flips and reparenting
- Attach scale-relative browser profiles and correct auto-layout fixture geometry
* fix(scene-graph): reject cyclic layer reorder
- Prevent reorderChild from parenting a node beneath its descendant
- Cover graph preservation after a rejected cyclic reorder
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