music indexer: 3s progress heartbeat log during a build

A long full rebuild logged only "resync started" then nothing until "done".
Add a console heartbeat (throttled to 3s, piggybacked on emitProgress) showing
folders/built/skipped/tracks/videos/posters/lyrics counts + the current path, so
progress is visible in the pm2 logs.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/servers/sidecar/music/indexer.ts

@@ -202,6 +202,7 @@ export function buildReport(s: IndexStatus = status): IndexReport {
 type ProgressListener = (s: IndexStatus) => void;
 const listeners = new Set<ProgressListener>();
 let lastEmit = 0;
+let lastLog = 0;
 
 export function onIndexProgress(cb: ProgressListener): () => void {
   listeners.add(cb);
@@ -211,6 +212,15 @@ export function onIndexProgress(cb: ProgressListener): () => void {
 /** Notify subscribers of progress; throttled to ~200ms unless `force` (e.g. terminal 'done'). */
 function emitProgress(force = false): void {
   const now = Date.now();
+  // Console heartbeat (throttled to 3s, independent of the SSE cadence) so a long build shows life.
+  if (now - lastLog >= 3000) {
+    lastLog = now;
+    console.log(
+      `[music] … ${status.foldersScanned} folders · ${status.albumsBuilt} built/${status.albumsSkipped} skipped · ` +
+        `${status.tracksIndexed} tracks · ${status.videosIndexed} videos · ${status.postersSaved} posters · ` +
+        `${status.lyricsIndexed} lyrics — ${status.currentPath}`,
+    );
+  }
   if (!force && now - lastEmit < 200) return;
   lastEmit = now;
   const snap = getIndexStatus();