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.

.gitignore

@@ -1,6 +1,5 @@
 tools/.env
 tools/.venv/
-assets/raw/
 node_modules/
 dist/
 .playwright-mcp/

README.md

@@ -40,7 +40,7 @@ npm test
 npm run dist
 ```
 
-`npm test` runs the smoke test. `npm run dist` packages the Windows Electron build as a zip in `dist/`.
+`npm test` runs the smoke test. `npm run dist` packages the Windows Electron build as a zip in `dist/`; `npm run dist:linux` produces a Linux AppImage in `dist/`. Every release ships both platforms.
 
 ## Documentation