1.0.1: target size for GIF / APNG / APNG preview

Frame-based exports (GIF, APNG, APNG-preview) accept an optional
target output size. ExportDialog exposes it as a single width
input above the three image-export rows; height is derived live
from the scene's aspect ratio so the user can't squash the output.
The preview HTML mirrors the target dims so a downsized export
previews at its real pixel size.

renderFrames takes targetWidth / targetHeight, sizes its canvas
accordingly and scales the ctx once; drawSceneFrame's own
save/restore preserves the transform across frames, including the
top-level-mask offscreen compositing path.

Target width on dialog open is inherited from the current
scene.canvas — watched via modelValue so resizing the stage and
reopening the dialog picks up the new size (instead of the stale
value from whenever ExportDialog first instantiated).

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

package.json

@@ -1,7 +1,7 @@
 {
   "name": "ruwio",
   "private": true,
-  "version": "1.0.0",
+  "version": "1.0.1",
   "type": "module",
   "scripts": {
     "dev": "vite",