fix: SpessaSynth init race condition, remove auto-load of sgm_v2.01

- Add _initInProgress flag to prevent concurrent init calls
- Remove auto-loadSoundFont from init (confuses user when loading DSK)
- SF3 loading happens only when user selects an instrument

app/static/js/services/soundfontPlayer.js

@@ -34,6 +34,7 @@
     // ── SpessaSynth integration state ──
     let _synthInstance = null;
     let _initialized = false;
+    let _initInProgress = false;
     let _currentSfId = null;
 
     const SonicSF = {
@@ -42,8 +43,11 @@
         // ── SpessaSynth init ──
         init: async function (audioContext) {
             if (_initialized && _synthInstance) return;
+            if (_initInProgress) return;
+            _initInProgress = true;
             if (!window.SpessaSynthClass || !window.__SpessaSynthCDN) {
                 console.warn("[SonicSF] SpessaSynth not loaded yet. Retrying in 2s...");
+                _initInProgress = false;
                 setTimeout(() => {
                     if (!_initialized && window.SpessaSynthClass && audioContext) {
                         this.init(audioContext);
@@ -52,20 +56,15 @@
                 return;
             }
             try {
-                // Register the AudioWorklet processor from CDN
                 const procUrl = window.__SpessaSynthCDN + "spessasynth_processor.min.js";
                 await audioContext.audioWorklet.addModule(procUrl);
-                // Create WorkletSynthesizer
                 _synthInstance = new window.SpessaSynthClass(audioContext);
-                // Wait for synth to be ready (loads default soundbank)
                 await _synthInstance.isReady;
                 _initialized = true;
+                _initInProgress = false;
                 console.log("[SonicSF] SpessaSynth initialized via AudioWorklet.");
-                // Auto-load default SF3
-                if (_currentSfId === null) {
-                    this.loadSoundFont("sgm_v2.01");
-                }
             } catch (e) {
+                _initInProgress = false;
                 console.warn("[SonicSF] SpessaSynth AudioWorklet init failed:", e, "- trying WorkerSynthesizer...");
                 try {
                     const mod = await import("https://esm.sh/spessasynth_lib@4.3.1");
@@ -74,7 +73,6 @@
                     await _synthInstance.isReady;
                     _initialized = true;
                     console.log("[SonicSF] SpessaSynth initialized via Worker.");
-                    if (_currentSfId === null) this.loadSoundFont("sgm_v2.01");
                 } catch (e2) {
                     console.error("[SonicSF] SpessaSynth init failed completely:", e2);
                 }