fix: SF3 download prefers SF2, cache invalidation on parse error

- Download endpoint reverses extension priority: .sf2 > .sf3
- loadSoundFont adds ?t= cache-buster, invalidates IndexedDB on error
- Retry logic: delete corrupted cache entry, allow re-download

app/static/js/services/soundfontPlayer.js

@@ -91,7 +91,7 @@
             }
             if (!buffer) {
                 try {
-                    const resp = await fetch("/api/v1/plugins/soundfonts/download/" + encodeURIComponent(sfId));
+                    const resp = await fetch("/api/v1/plugins/soundfonts/download/" + encodeURIComponent(sfId) + "?t=" + Date.now());
                     if (!resp.ok) throw new Error("Download failed: " + resp.status);
                     buffer = await resp.arrayBuffer();
                     if (window.SonicSFStorage) {
@@ -107,7 +107,18 @@
                 _currentSfId = sfId;
                 console.log("[SonicSF] SoundFont loaded:", sfId);
             } catch (e) {
-                console.error("[SonicSF] Error parsing SF in SpessaSynth:", e);
+                console.error("[SonicSF] Error parsing SF in SpessaSynth:", sfId, e);
+                // Invalidate cache and retry once with fresh download
+                if (window.SonicSFStorage) {
+                    try {
+                        const db = await window.SonicSFStorage.openDB();
+                        const tx = db.transaction(window.SonicSFStorage.storeName, "readwrite");
+                        tx.objectStore(window.SonicSFStorage.storeName).delete(sfId);
+                        console.log("[SonicSF] Invalidated cache for:", sfId);
+                    } catch (ce) {}
+                }
+                // Clear current SF so next load will actually run
+                _currentSfId = null;
             }
         },