feat: accept space, &, / as artist separators in metadata editor

- Space as fallback separator on save when no explicit separator present
  (Artist1 Artist2 → Artist1;Artist2)
- & and / added to explicit separator set everywhere
- navidromeArtist (download path) also handles /

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

backend/lib/metadata.js

@@ -13,6 +13,7 @@ function navidromeArtist(name) {
     .replace(/\s+ft\.?\s+/gi, ';')
     .replace(/\s+featuring\s+/gi, ';')
     .replace(/\s+&\s+/g, ';')
+    .replace(/\s*\/\s*/g, ';')
     .replace(/,\s*/g, ';');
 }
 

backend/novasonic-server.js

@@ -244,7 +244,10 @@ app.post('/api/spotify/resolve', async (req, res) => {
 // and rejoins with the canonical sep ("; " for track artist, ", " for album artist).
 function _normalizeArtists(str, sep) {
   if (!str) return str;
-  return str.split(/\s*[•·;,]\s*/).map(s => s.trim()).filter(Boolean).join(sep);
+  // If an explicit separator is present use it; otherwise fall back to splitting on spaces
+  // so the user can type "Artist1 Artist2" without a semicolon.
+  const splitter = /[•·;,&/]/.test(str) ? /\s*[•·;,&/]\s*/ : /\s+/;
+  return str.split(splitter).map(s => s.trim()).filter(Boolean).join(sep);
 }
 
 // Strip " - Topic" suffix YouTube Music appends to artist channel names

src/ui.js

@@ -240,7 +240,7 @@ document.addEventListener('click', e => {
 // Track artist → "Serph; Zun"  |  Album artist → "Serph, Zun"
 function _fmtArtists(str, sep) {
   if (!str) return '';
-  return str.split(/\s*[•·;,]\s*/).map(s => s.trim()).filter(Boolean).join(sep);
+  return str.split(/\s*[•·;,&/]\s*/).map(s => s.trim()).filter(Boolean).join(sep);
 }
 
 function _renderInfoModal(s) {