fix(studio): address family B timeline review findings

- revert diamond selection when a rejected retime leaves the source in place
- clear project-local ease focus and expansion on player store reset
- share one static-position-hold predicate across the tween cache
- invalidate the GSAP cache even when a group timing rewrite throws
- stamp each lane keyframe's ease from its own source tween
- memoize property lanes and row offsets so memo'd diamond lanes hold
- use the editable tween duration for drag position commits
- restore the pre-t=0 pad in the all-collapsed content origin
- clamp the drag ghost and drop placeholder to the collapsed clip height
- aria-expanded on the layer disclosure, aria-pressed plus state-specific
  labels on the keyframe toggle, 24px chevron targets, focus-visible parity

packages/studio/src/components/editor/KeyframeEaseList.tsx

@@ -93,7 +93,11 @@ export function KeyframeEaseList({
           ? "Custom"
           : (EASE_LABELS[segEase] ?? segEase);
         return (
-          <div key={`${i}-${kf.percentage}`} className="rounded-md bg-neutral-900/50">
+          <div
+            key={`${i}-${kf.percentage}`}
+            data-ease-segment-pct={kf.percentage}
+            className="rounded-md bg-neutral-900/50"
+          >
             <button
               type="button"
               onClick={() => onToggle(isExpanded ? null : kf.percentage)}