feat(studio): add Layers panel as new inspector tab (#784)

* feat(studio): add Layers panel as new inspector tab

Adds a dedicated Layers tab alongside Design and Renders in the right
panel inspector. The panel shows the full composition element tree with
collapsible hierarchy — clicking a layer selects it without navigating
away from the tree view.

Closes #783

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat(studio): add visual element previews to Layers panel

Each layer row now shows a small color/content preview thumbnail:
- Text elements show a snippet of their content in the actual font color
- Container elements show their background color as a colored swatch
- Image elements show a tiny thumbnail of the image
- Media elements show an icon indicator

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat(studio): add hover-to-highlight and auto-seek to Layers panel

Replace tiny preview thumbnails with hover highlighting — hovering a
layer row highlights the element in the preview canvas. Clicking a layer
auto-seeks the playhead to that element's start time in the timeline.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(studio): layers panel tab order, autoseek, and renders toolbar overflow

- Reorder inspector tabs to Design → Layers → Renders
- Fix autoseek: walk DOM ancestors when selected element has no direct
  timeline match, so clicking a child like S2 Heading correctly seeks
  to the start of its parent scene
- Fix Renders toolbar overflow: add flex-wrap to the export controls
  header so selects and the Export button wrap instead of clipping

* fix(studio): seek to midpoint of element duration in layers panel autoseek

* fix(studio): layers panel seek now drives adapter.seek via requestSeek signal

setCurrentTime() only updated the store — adapter.seek() and liveTime.notify()
were never called so the iframe never moved. Add requestedSeekTime to the player
store; useTimelinePlayer subscribes and calls the real seek() path when it fires.

* feat(studio): hover over a layer auto-seeks to element midpoint (300ms debounce)

* feat(studio): add collapsible sections to Design panel

Section component now supports collapse/expand with a chevron toggle.
Text, Layout, and Fill sections stay expanded by default. Less-used
sections (Flex, Radius, Stroke, Effects, Clip, Transparency) start
collapsed to reduce scrolling.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(studio): remove stale selectedTimelineElement usages dropped in rebase

* fix(studio): stabilize resetErrors in useConsoleErrorCapture to break render loop

resetErrors was a new function object on every render. handlePreviewIframeRef
had it as a dep, so it also changed every render. NLELayout's useEffect watching
onIframeRef would re-fire, calling setPreviewIframe again, which re-ran
useConsoleErrorCapture with the new iframe — infinite loop.

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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

@@ -1,4 +1,4 @@
-import { useRef, useCallback } from "react";
+import { useRef, useCallback, useEffect } from "react";
 import { usePlayerStore, liveTime, type TimelineElement } from "../store/playerStore";
 import { useMountEffect } from "../../hooks/useMountEffect";
 import { usePlaybackKeyboard } from "./usePlaybackKeyboard";
@@ -327,6 +327,16 @@ export function useTimelinePlayer() {
     [getAdapter, setCurrentTime, setIsPlaying, stopRAFLoop, stopReverseLoop],
   );
 
+  // Handle seek requests from outside the player loop (e.g. LayersPanel).
+  useEffect(() => {
+    return usePlayerStore.subscribe((state, prev) => {
+      if (state.requestedSeekTime !== null && state.requestedSeekTime !== prev.requestedSeekTime) {
+        seek(state.requestedSeekTime);
+        usePlayerStore.getState().clearSeekRequest();
+      }
+    });
+  }, [seek]);
+
   const { playbackKeyDownRef, playbackKeyUpRef, attachIframeShortcutListeners, togglePlay } =
     usePlaybackKeyboard({
       iframeRef,