feat: add studio timeline editing (#390)

## Summary

Add the actual Studio timeline editing layer on top of the preview/runtime foundation.

This PR includes:

- drag-to-move clips across time and tracks
- left/right resize handles with media-aware trim persistence
- edge auto-scroll and edge track creation while dragging
- selector-based source patching for `data-start`, `data-duration`, `data-track-index`, `z-index`, and media trim attributes
- timeline UI cleanup, theming, hover/drag states, and the `Copy Prompt` action

## Why This PR Is Separate

This is the user-facing editing behavior. It depends on the preview/runtime fixes in the base PR, but it is much easier to review once that plumbing is isolated.

## Verification

- `bun run --filter @hyperframes/studio test`
- `bun run --filter @hyperframes/studio typecheck`
- `bunx oxlint packages/studio/src/App.tsx packages/studio/src/components/nle/NLELayout.tsx packages/studio/src/player/components/EditModal.tsx packages/studio/src/player/components/Timeline.tsx packages/studio/src/player/components/TimelineClip.tsx packages/studio/src/player/components/timelineEditing.ts packages/studio/src/player/components/timelineEditing.test.ts packages/studio/src/player/components/timelineTheme.ts packages/studio/src/player/components/timelineTheme.test.ts packages/studio/src/utils/sourcePatcher.ts packages/studio/src/utils/sourcePatcher.test.ts`
- `bunx oxfmt --check packages/studio/src/App.tsx packages/studio/src/components/nle/NLELayout.tsx packages/studio/src/player/components/EditModal.tsx packages/studio/src/player/components/Timeline.tsx packages/studio/src/player/components/TimelineClip.tsx packages/studio/src/player/components/timelineEditing.ts packages/studio/src/player/components/timelineEditing.test.ts packages/studio/src/player/components/timelineTheme.ts packages/studio/src/player/components/timelineTheme.test.ts packages/studio/src/utils/sourcePatcher.ts packages/studio/src/utils/sourcePatcher.test.ts`

## Browser Proof

- verified timeline drag / resize / trim flows in Studio with `agent-browser`
- verified preview hot-refresh behavior without iframe remount flashes

## Stack

- depends on #389
- followed by `fix: smooth scrubber end seeking`

[result.mp4 <span class="graphite__hidden">(uploaded via Graphite)</span> <img class="graphite__hidden" src="https://app.graphite.com/user-attachments/thumbnails/ca71c177-5042-468d-906f-b353938f40f8.mp4" />](https://app.graphite.com/user-attachments/video/ca71c177-5042-468d-906f-b353938f40f8.mp4)

packages/studio/src/components/nle/NLELayout.tsx

@@ -27,6 +27,15 @@ interface NLELayoutProps {
     element: TimelineElement,
     style: { clip: string; label: string },
   ) => ReactNode;
+  /** Persist timeline move actions back into source HTML */
+  onMoveElement?: (
+    element: TimelineElement,
+    updates: Pick<TimelineElement, "start" | "track">,
+  ) => Promise<void> | void;
+  onResizeElement?: (
+    element: TimelineElement,
+    updates: Pick<TimelineElement, "start" | "duration" | "playbackStart">,
+  ) => Promise<void> | void;
   /** Exposes the compIdToSrc map for parent components (e.g., useRenderClipContent) */
   onCompIdToSrcChange?: (map: Map<string, string>) => void;
   /** Whether the timeline panel is visible (default: true) */
@@ -50,6 +59,8 @@ export const NLELayout = memo(function NLELayout({
   onIframeRef,
   onCompositionChange,
   renderClipContent,
+  onMoveElement,
+  onResizeElement,
   onCompIdToSrcChange,
   timelineVisible,
   onToggleTimeline,
@@ -379,6 +390,8 @@ export const NLELayout = memo(function NLELayout({
                 onSeek={seek}
                 onDrillDown={handleDrillDown}
                 renderClipContent={renderClipContent}
+                onMoveElement={onMoveElement}
+                onResizeElement={onResizeElement}
               />
             </div>
             {timelineFooter && <div className="flex-shrink-0">{timelineFooter}</div>}