feat(studio): timeline inline expansion + __clipTree runtime primitive

When a child element inside a sub-composition is selected, the timeline
replaces the parent scene clip with the deepest-level siblings. Deselect
or selecting outside collapses back. Expanded clips are fully editable —
move, resize, delete, and split — addressed by their real DOM id with
timeline time rebased onto the sub-comp they live in.

Runtime:
- New window.__clipTree API: a read-only hierarchical ClipNode tree
  (id/parentId/children + backing element) so Studio can derive
  parent/child relationships for inline expansion.

Studio:
- useExpandedTimelineElements derives the expanded view from
  selectedElementId + clipParentMap (pure useMemo, no useEffect).
  Each child rebases onto its immediate sub-comp host (start +
  sourceFile), so multi-level nesting targets the right file.
- NLELayout routes expanded-clip edits through the same handlers
  top-level clips use, in local coordinates — edits save to the
  sub-comp source and reflect via reloadPreview (no separate DOM-patch
  path). This is the canonical update; there is no reactive observer.
- findMatchingTimelineElementId resolves sub-comp children with no
  top-level element to `sourceFile#id`.
- Razor tool enabled by default; studio_razor_split analytics event
  fired on single and split-all.
- O(n²) isElementGsapTargeted extracted to gsapTargetCache.ts with a
  cached Set+WeakSet O(1) lookup.

packages/studio/src/player/hooks/useTimelineSyncCallbacks.ts

@@ -66,6 +66,8 @@ export function useTimelineSyncCallbacks({
         return;
       }
 
+      usePlayerStore.getState().setClipManifest(data.clips);
+
       // Show root-level clips: no parentCompositionId, OR parent is a "phantom wrapper"
       const clipCompositionIds = new Set(data.clips.map((c) => c.compositionId).filter(Boolean));
       const filtered = data.clips.filter(
@@ -77,6 +79,26 @@ export function useTimelineSyncCallbacks({
       } catch {
         iframeDoc = null;
       }
+
+      try {
+        const iframeWin = iframeRef.current?.contentWindow as
+          | (Window & { __clipTree?: import("@hyperframes/core/runtime/clipTree").ClipTree })
+          | null;
+        const clipTree = iframeWin?.__clipTree;
+        if (clipTree) {
+          const parentMap = new Map<string, string>();
+          const walk = (nodes: typeof clipTree.roots) => {
+            for (const node of nodes) {
+              if (node.id && node.parentId) parentMap.set(node.id, node.parentId);
+              if (node.children.length > 0) walk(node.children);
+            }
+          };
+          walk(clipTree.roots);
+          usePlayerStore.getState().setClipParentMap(parentMap);
+        }
+      } catch {
+        // cross-origin or __clipTree not available — parentMap stays empty
+      }
       const usedHostEls = new Set<Element>();
       const els: TimelineElement[] = filtered.map((clip, index) => {
         const hostEl = iframeDoc