* feat(studio): timeline collision and placement model
What: new pure module timelineCollision — zone-aware drop placement
(clampTrackToZone, resolveZoneDropPlacement, resolveInsertRow,
resolvePlacement, lane/overlap predicates) with its full test suite.
Why: the no-overlap core of the NLE clip-drag engine; plain functions, no
DOM, no React, no store writes.
How: new files only; type-only imports from the existing playerStore.
First runtime consumer arrives with the drag-engine PRs.
Test plan: bunx vitest run timelineCollision.test.ts; tsc --noEmit; fallow
audit clean (all exports test-consumed).
* feat(studio): timeline magnetic snapping
What: new pure module timelineSnapping — snap-target collection and
pixel-threshold time snapping (collectTimelineSnapTargets, snapTimelineTime,
snapMoveToTargets) with tests.
Why: the magnet math for clip drags/trims, reviewable standalone.
How: new files only; type-only playerStore imports; consumers land with the
drag engine.
Test plan: bunx vitest run timelineSnapping.test.ts; tsc --noEmit; fallow
audit clean.
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Co-authored-by: ukimsanov <ular.kimsanov@heygen.com>
