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/player/components/LayerDisclosureRow.tsx

@@ -31,6 +31,7 @@ export function LayerDisclosureRow({
     >
       <button
         type="button"
+        aria-expanded={isExpanded}
         aria-label={`${isExpanded ? "Collapse" : "Expand"} ${name} keyframes`}
         title={`${isExpanded ? "Collapse" : "Expand"} keyframe lanes`}
         className="flex h-5 w-4 shrink-0 items-center justify-center rounded border-0 bg-transparent p-0 text-white/55 hover:text-white focus-visible:outline focus-visible:outline-1 focus-visible:outline-[#3CE6AC]"
@@ -47,10 +48,9 @@ export function LayerDisclosureRow({
           style={{ transform: isExpanded ? "rotate(90deg)" : undefined }}
         />
       </button>
-      <span
-        aria-label="Layer keyframe indicator"
-        className="shrink-0 text-[13px] leading-none text-white/40"
-      >
+      {/* Decorative: the disclosure button above already names the row's keyframe
+          state, and aria-label on a plain span is not exposed reliably anyway. */}
+      <span aria-hidden="true" className="shrink-0 text-[13px] leading-none text-white/40">
         ◇
       </span>
       <span className="min-w-0 flex-1 truncate font-medium" title={name}>