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.

agent/agent.py

@@ -213,10 +213,13 @@ SYSTEM_PROMPT = textwrap.dedent("""\
     - Ambiguous results → offer_song_choices with the top 2-3 options, name
       them briefly, and let the user pick by voice or in the player panel.
       Never start playback on a guess.
-    The library is permanent: list_library shows what is already downloaded,
-    and those tracks play instantly without searching. If the user names a
-    library track exactly, just play it. Control playback with pause_music,
-    resume_music, skip_song and seek_music; check what's on with now_playing.
+    Prefer what is already saved: search_music puts downloaded library
+    matches first (in_library=true) — always pick one of those over a fresh
+    YouTube result, and list_library shows the whole saved collection which
+    plays instantly. If the user names a library track exactly, just play it.
+    A brand-new song starts playing within seconds and finishes downloading
+    in the background. Control playback with pause_music, resume_music,
+    skip_song and seek_music; check what's on with now_playing.
     add_stream registers a live radio or direct audio URL as a library track.
     While music is playing you cannot hear the user — they will come back to
     you when they want to talk again, and the music pauses automatically.

agent/media_mcp.py

@@ -69,27 +69,30 @@ def _fmt_duration(seconds) -> str:
 
 @mcp.tool()
 def search_music(query: str, limit: int = 5) -> str:
-    """Search YouTube Music for songs. Call this before playing anything the
-    user describes by name, artist or lyrics. Returns JSON results with
-    video_id, title, channel, duration and in_library flags. Pick the result
-    that clearly matches what the user asked for; if two or more could be
-    right, use offer_song_choices instead of guessing."""
+    """Search for songs: already-downloaded library matches come first, then
+    YouTube Music results. Call this before playing anything the user
+    describes by name, artist or lyrics. Results carry video_id, title,
+    channel, duration and in_library flags. ALWAYS prefer a result with
+    in_library=true — it is already saved and plays instantly. Pick the
+    result that clearly matches what the user asked for; if two or more could
+    be right, use offer_song_choices instead of guessing."""
     data = _media_post("/media/api/search", {"query": query, "limit": max(1, min(limit, 10))})
     if "error" in data:
         return f"Search failed: {data['error']}"
     results = data.get("results", [])
     if not results:
-        return f"No YouTube Music results for '{query}'."
+        return f"No results for '{query}'."
     return json.dumps(results, ensure_ascii=False)
 
 
 @mcp.tool()
 def play_song(video_id: str, title: str = "", channel: str = "") -> str:
     """Play a song in the user's web player. Pass the video_id from
-    search_music (or an in_library track_id). Downloads and transcodes first
-    if needed; playback starts automatically once ready. After calling this,
-    tell the user what is playing in one short sentence and stop talking —
-    the player takes over and the conversation pauses until they return."""
+    search_music — for an in_library result this plays the saved copy with no
+    download; a new song downloads and starts playing automatically while it
+    arrives. After calling this, tell the user what is playing in one short
+    sentence and stop talking — the player takes over and the conversation
+    pauses until they return."""
     data = _media_post("/media/api/play", {
         "room": MEDIA_ROOM, "video_id": video_id, "title": title, "channel": channel,
     })
@@ -100,9 +103,9 @@ def play_song(video_id: str, title: str = "", channel: str = "") -> str:
     name = track.get("title") or title or video_id
     if status == "downloading":
         return (
-            f"'{name}' is downloading and will start playing automatically when "
-            "ready (usually under a minute). Say it's on the way, then hand over "
-            "to the player."
+            f"'{name}' is downloading and starts playing within seconds — "
+            "audio streams in while the download finishes. Say it's on the "
+            "way, then hand over to the player."
         )
     return f"Playing '{name}' now. Hand over to the player with a short sign-off."