feat: progressive music streaming, library-first search, player fixes

- Stream downloads as they grow: raw best-audio (no mp3 transcode) served
  chunked from the stream endpoint mid-download, then with native Range
  once complete. Songs play within seconds of hitting Play.
- Fix searched songs never starting: reconcileMedia now wires the stream
  URL when a track that was preparing gains one; audio_url is stable for
  the whole lifecycle so the player never reloads mid-playback.
- Progress bars now parse yt-dlp stderr (stdout never carried [download]).
- Prefer downloaded songs: /media/api/search merges ready library matches
  ahead of YouTube results; search_music/play_song tooling and the agent
  prompt tell Hope to always pick in_library=true.
- Mute button turns solid red while the mic is muted.

web/app.js

@@ -1207,7 +1207,15 @@ function reconcileMedia(s) {
     const pendingJob = (s.pending || []).find(j => !track || j.track_id === track.id);
     updateMediaProgress(track, pendingJob);
 
-    if (track && track.id !== mediaCurrentTrackId) loadMediaTrack(track);
+    if (track && track.id !== mediaCurrentTrackId) {
+        loadMediaTrack(track);
+    } else if (track && track.audio_url && mediaAudio.getAttribute("src") !== track.audio_url) {
+        // The track was loaded before it had a stream (still downloading) and
+        // now has one — wire it up so playback can start without a reload.
+        mediaAudio.src = track.audio_url;
+        mediaAudio.load();
+        updateMediaNowCard(track);
+    }
     if (!track && mediaCurrentTrackId && s.desired === "stopped") clearMediaAudio();
 
     applyDesiredMediaState(s, track);
@@ -1224,7 +1232,9 @@ function reconcileMedia(s) {
 
 function applyDesiredMediaState(s, track) {
     if (s.desired === "playing") {
-        if (track && track.status === "ready" && mediaAudio.src && mediaAudio.paused) {
+        // audio_url presence means a playable stream exists — including a
+        // still-growing download, which plays progressively.
+        if (track && track.audio_url && mediaAudio.src && mediaAudio.paused) {
             mediaAudio.play().catch((e) => console.warn("playback blocked:", e));
         }
     } else if (!mediaAudio.paused) {
@@ -1235,14 +1245,14 @@ function applyDesiredMediaState(s, track) {
 function loadMediaTrack(track) {
     mediaCurrentTrackId = track.id;
     updateMediaNowCard(track);
-    if (track.audio_url && (track.kind === "stream" || track.status === "ready")) {
+    if (track.audio_url) {
         if (mediaAudio.getAttribute("src") !== track.audio_url) {
             mediaAudio.src = track.audio_url;
             mediaAudio.load();
         }
     } else {
-        // Downloading or failed: no stream yet. The poll flips this to the
-        // real URL once status turns "ready".
+        // Downloading or failed: no stream yet. reconcileMedia wires the
+        // stream URL in via polling as soon as one is available.
         mediaAudio.removeAttribute("src");
         mediaAudio.load();
         updateMediaControls();
@@ -1266,7 +1276,9 @@ function updateMediaNowCard(track) {
     if (track.status === "failed") {
         mediaChannelEl.textContent = "Download failed — pick another result or try again.";
     } else if (track.status === "downloading") {
-        mediaChannelEl.textContent = "Preparing…";
+        // Progressive streaming: the track plays while the download runs.
+        mediaChannelEl.textContent = track.channel
+            ? `${track.channel} · downloading` : "Downloading…";
     } else {
         mediaChannelEl.textContent = track.channel || (track.kind === "stream" ? "Live stream" : "");
     }
@@ -1288,9 +1300,7 @@ function updateMediaProgress(track, job) {
     mediaProgressWrap.hidden = false;
     const pct = Math.round(job.progress || 0);
     mediaProgressFill.style.width = `${pct}%`;
-    const stage = job.stage === "transcoding"
-        ? "Re-encoding…"
-        : job.stage === "queued" ? "Queued…" : "Downloading…";
+    const stage = job.stage === "queued" ? "Queued…" : "Downloading…";
     mediaProgressLabel.textContent = `${stage} ${pct}%`;
     if (track) updateMediaNowCard(track);
 }