0.16.0: animated GIF / APNG export + transparent canvas

- New frame-by-frame export pipeline in src/lib/frameExport.ts: loads
  scene images, walks rangeIn..rangeOut at scene.fps, drawSceneFrame
  to an offscreen canvas, awaits a per-frame callback, yields every
  4 frames to keep progress responsive, honours AbortSignal.
- Animated GIF via gifenc (per-frame quantize/palette, ~5 KB lib).
- Animated PNG via UPNG.js + pako (lossless RGBA, alpha-aware, ~30 KB).
- drawSceneFrame now clearRects first and skips the background fill
  when scene.canvas.background === 'transparent' — prerequisite for
  the alpha to reach the APNG output.
- DocumentDrawer: new checkerboard toggle next to the colour picker
  flips the stage between its last-picked colour and transparent;
  disabled swatch + 'Transparent' hex label make the state obvious.
- ExportDialog: three new option rows — Animated GIF, Animated PNG,
  and an APNG preview page that bundles the rendered APNG into a
  standalone HTML with a checkerboard backdrop + dark/light toggles
  for verifying transparency at a glance.
- Tests: renderFrames frame count + abort, GIF header magic, APNG
  acTL presence, transparent round-trip (decoded alpha == 0 on
  un-painted pixels), preview HTML structure, and the two UI tests
  covering ExportDialog's new rows and the progress-view transition.

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

package-lock.json

@@ -1,16 +1,18 @@
 {
-  "name": "animatr",
-  "version": "0.0.0",
+  "name": "ruwio",
+  "version": "0.15.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
-      "name": "animatr",
-      "version": "0.0.0",
+      "name": "ruwio",
+      "version": "0.15.0",
       "dependencies": {
         "@phosphor-icons/vue": "^2.2.1",
+        "gifenc": "^1.0.3",
         "konva": "^9.3.16",
         "pinia": "^2.2.6",
+        "upng-js": "^2.1.0",
         "vue": "^3.5.13",
         "vue-konva": "^3.1.2"
       },
@@ -1210,6 +1212,12 @@
         "node": "^8.16.0 || ^10.6.0 || >=11.0.0"
       }
     },
+    "node_modules/gifenc": {
+      "version": "1.0.3",
+      "resolved": "https://registry.npmjs.org/gifenc/-/gifenc-1.0.3.tgz",
+      "integrity": "sha512-xdr6AdrfGBcfzncONUOlXMBuc5wJDtOueE3c5rdG0oNgtINLD+f2iFZltrBRZYzACRbKr+mSVU/x98zv2u3jmw==",
+      "license": "MIT"
+    },
     "node_modules/he": {
       "version": "1.2.0",
       "resolved": "https://registry.npmjs.org/he/-/he-1.2.0.tgz",
@@ -1290,6 +1298,12 @@
         "node": "^10 || ^12 || ^13.7 || ^14 || >=15.0.1"
       }
     },
+    "node_modules/pako": {
+      "version": "1.0.11",
+      "resolved": "https://registry.npmjs.org/pako/-/pako-1.0.11.tgz",
+      "integrity": "sha512-4hLB8Py4zZce5s4yd9XzopqwVv/yGNhV1Bl8NTmCq1763HeK2+EwVTv+leGeL13Dnh2wfbqowVPXCIO0z4taYw==",
+      "license": "(MIT AND Zlib)"
+    },
     "node_modules/path-browserify": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/path-browserify/-/path-browserify-1.0.1.tgz",
@@ -1458,6 +1472,15 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/upng-js": {
+      "version": "2.1.0",
+      "resolved": "https://registry.npmjs.org/upng-js/-/upng-js-2.1.0.tgz",
+      "integrity": "sha512-d3xzZzpMP64YkjP5pr8gNyvBt7dLk/uGI67EctzDuVp4lCZyVMo0aJO6l/VDlgbInJYDY6cnClLoBp29eKWI6g==",
+      "license": "MIT",
+      "dependencies": {
+        "pako": "^1.0.5"
+      }
+    },
     "node_modules/vite": {
       "version": "6.4.2",
       "resolved": "https://registry.npmjs.org/vite/-/vite-6.4.2.tgz",