Add JamesDSP playback controls and verification harness

frontend/vendor/jamesdsp/worklet.mjs

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
-const engineURL=new URLSearchParams(new URL(import.meta.url).hash.slice(1)).get('engine');
-if(!engineURL) throw new Error('JamesDSP engine asset URL is missing');
-const {default:createJamesDSP}=await import(engineURL);
+// AudioWorkletGlobalScope does not support dynamic import; this immutable
+// vendor path is versioned with the upstream pin and remapped by the SW cache.
+import createJamesDSP from './dsp/jamesdsp-77be0b2.mjs';
 class JamesDSPProcessor extends AudioWorkletProcessor {
   constructor(options) {
     super(); this.closed=false;this.failed=false;