fix: SC metadata fields, albumartist & separator, importer clear, folder rename on album edit

- SC tracks: use artworkUrl/album/genre fields (not iTunes artworkUrl100/collectionName/primaryGenreName)
- Playlist handler: same SC field fallbacks for artwork, album, genre, year
- ytdlp.js: convert & to , in album_artist tag so Navidrome albumartist.Split works
- Importer: clear both previews on any URL input change, not just on clear
- edit-metadata: rename album folder on disk when album name changes

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/spotify.js

@@ -7,6 +7,11 @@ import { openDlModal } from './ui.js';
 
 // ─── UNIFIED IMPORTER INPUT ───
 export function onImporterInput(val) {
+  // Always clear results when URL changes
+  document.getElementById('spotify-preview').style.display = 'none';
+  document.getElementById('sc-preview').style.display = 'none';
+  document.getElementById('importer-hint').style.display = val ? 'none' : '';
+
   const badge = document.getElementById('importer-badge');
   const btn   = document.getElementById('importer-btn');
   if (!badge || !btn) return;
@@ -32,12 +37,6 @@ export function onImporterInput(val) {
     btn.style.color = '';
     btn.style.borderColor = '';
   }
-  // Hide results when input is cleared
-  if (!val) {
-    document.getElementById('spotify-preview').style.display = 'none';
-    document.getElementById('sc-preview').style.display = 'none';
-    document.getElementById('importer-hint').style.display = '';
-  }
 }
 
 export async function resolveImporterLink() {