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.

js/sfxbank.js

@@ -111,7 +111,7 @@ const SfxBank = {
     if (this.buffers.has(name) || this.pending.has(name) || this.failed.has(name)) return;
     const file = this.FILES[name];
     if (!file || !this.ctx || typeof fetch !== 'function') return;
-    const job = fetch('/assets/sfx/' + encodeURIComponent(file) + '?v=54')
+    const job = fetch('/assets/sfx/' + encodeURIComponent(file) + '?v=55')
       .then(r => { if (!r.ok) throw new Error('HTTP ' + r.status); return r.arrayBuffer(); })
       .then(bytes => this.ctx.decodeAudioData(bytes))
       .then(buffer => this.buffers.set(name, this.trim(buffer)))