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/components/editor/PropertyPanel.tsx

@@ -1,4 +1,4 @@
-import { memo, useEffect, useRef, useState } from "react";
+import { memo, useEffect, useMemo, useRef, useState } from "react";
 import { Eye, Layers, Move, X } from "../../icons/SystemIcons";
 import { useStudioShellContext } from "../../contexts/StudioContext";
 import { readStudioBoxSize, readStudioPathOffset, readStudioRotation } from "./manualEdits";
@@ -111,6 +111,29 @@ export const PropertyPanel = memo(function PropertyPanel({
   const cacheElementKey = element?.id ?? element?.selector ?? "";
   const cacheEntry = usePlayerStore((s) => s.keyframeCache.get(cacheElementKey));
 
+  const iframeRef = previewIframeRef ?? { current: null };
+  const gsapAnimIdForMemo = element
+    ? (gsapAnimations?.find((a: { keyframes?: unknown }) => a.keyframes)?.id ??
+      gsapAnimations?.[0]?.id ??
+      null)
+    : null;
+  const gsapRuntimeValues = useMemo(
+    () =>
+      element
+        ? readGsapRuntimeValuesForPanel(gsapAnimIdForMemo, gsapAnimations, element, iframeRef)
+        : null,
+    // eslint-disable-next-line react-hooks/exhaustive-deps -- iframeRef is stable; currentTime drives re-reads during playback
+    [gsapAnimIdForMemo, gsapAnimations, element, currentTime],
+  );
+  const gsapBorderRadius = useMemo(
+    () =>
+      element
+        ? readGsapBorderRadiusForPanel(gsapRuntimeValues, gsapAnimations, element, iframeRef)
+        : null,
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+    [gsapRuntimeValues, gsapAnimations, element, currentTime],
+  );
+
   if (!element) {
     return (
       <div className="flex h-full flex-col bg-neutral-900">
@@ -194,21 +217,6 @@ export const PropertyPanel = memo(function PropertyPanel({
     return gsapAnimId ?? "";
   };
 
-  // Read ALL GSAP-interpolated values at the current seek time.
-  const gsapRuntimeValues = readGsapRuntimeValuesForPanel(
-    gsapAnimId,
-    gsapAnimations,
-    element,
-    previewIframeRef ?? { current: null },
-  );
-
-  const gsapBorderRadius = readGsapBorderRadiusForPanel(
-    gsapRuntimeValues,
-    gsapAnimations,
-    element,
-    previewIframeRef ?? { current: null },
-  );
-
   const displayX = gsapRuntimeValues?.x ?? manualOffset.x;
   const displayY = gsapRuntimeValues?.y ?? manualOffset.y;
   const displayW = gsapRuntimeValues?.width ?? resolvedWidth;

packages/studio/src/components/editor/manualEditingAvailability.ts

@@ -73,7 +73,7 @@ export const STUDIO_KEYFRAMES_ENABLED = resolveStudioBooleanEnvFlag(
 export const STUDIO_RAZOR_TOOL_ENABLED = resolveStudioBooleanEnvFlag(
   env,
   ["VITE_STUDIO_ENABLE_RAZOR_TOOL", "VITE_STUDIO_RAZOR_TOOL_ENABLED"],
-  false,
+  true,
 );
 
 // When disabled (the default), drag/resize/rotate commits always take the CSS