0.5.6: show/hide locked tracks + group lock + crop/mask-preview split

- Timeline: new show/hide toggle next to snap; locked tracks (including
  layer, clip, and the new group lock) are filtered from the timeline
  when the toggle is off. Preference lives in localStorage and is
  shared across components via a module-level ref.
- Groups become lockable via the same inline lock toggle. A locked
  group propagates to its children: they behave as effectively locked
  in the timeline and on the stage. Collapse/expand still works on a
  locked group.
- Canvas: layers in locked+hidden tracks render as a 1px outline in
  the layer (or fill) color instead of their full fill, and are
  draggable:false / listening:false. Mask layers keep their dashed
  ghost styling; masks still apply in the preview overlay regardless
  of lock or show state.
- drawSceneFrame gains an optional `{ crop }` option; the mask-preview
  overlay passes the editor's crop toggle through, so the two controls
  are fully independent. Crop changes now also trigger a preview
  redraw via a watcher dep.
- Tests: new suites for show-locked persistence, group lock store
  action, crop option on drawSceneFrame (including mask+crop combos).
  Properties transparent-toggle tests now reset the section prefs
  localStorage so the Appearance section is guaranteed open when the
  panel mounts.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/render.ts

@@ -333,14 +333,18 @@ export function drawSceneFrame(
   scene: Scene,
   time: number,
   images: Record<string, HTMLImageElement>,
+  options?: { crop?: boolean },
 ) {
   const lw = scene.canvas.width
   const lh = scene.canvas.height
+  const crop = options?.crop !== false
 
   ctx.save()
-  ctx.beginPath()
-  ctx.rect(0, 0, lw, lh)
-  ctx.clip()
+  if (crop) {
+    ctx.beginPath()
+    ctx.rect(0, 0, lw, lh)
+    ctx.clip()
+  }
   ctx.fillStyle = scene.canvas.background
   ctx.fillRect(0, 0, lw, lh)