1.0.0: delete-group cascade + native-size APNG preview

First stable release. Highlights in this bump:

- Group context menu gains a proper danger "Delete group" entry
  that tears down the group AND every track it contains (layers,
  clip tracks, script tracks, audio tracks) along with their
  dependent content. "Ungroup" keeps its old meaning as a separate
  non-danger item, so the two operations stop being confusable.
  New removeTrackGroupWithChildren store action clears any
  selection pointing inside the group before dispatching per-kind
  removes.
- APNG preview page now renders the export at its native pixel
  size: the .stage + <img> use explicit width/height in pixels
  instead of a max-960 aspect-ratio box with object-fit: contain.
  A 4K export looks 4K; the body scrolls if the window is
  smaller.

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

package.json

@@ -1,7 +1,7 @@
 {
   "name": "ruwio",
   "private": true,
-  "version": "0.18.3",
+  "version": "1.0.0",
   "type": "module",
   "scripts": {
     "dev": "vite",