release: bump to 0.8.0 (HD Remaster) with docs, cache bust, and smoke coverage

Cache-bust v=54 -> v=55 across index.html and sfxbank.js, bump the game
version to 0.8.0, document the HD Remaster setting in gameplay.md and the
changelog, and extend the smoke suite with 4x sheet-geometry bounds checks,
HD loader fallback URL assertions, and toggle persistence/reload checks.

package.json

@@ -1,7 +1,7 @@
 {
   "name": "meatslicer",
   "productName": "MeatSlicer",
-  "version": "0.7.2",
+  "version": "0.8.0",
   "private": true,
   "description": "A Butcher's Descent - clear, harvest, descend.",
   "main": "desktop/main.js",