fix: kept file protection, skip/autoplay, TTS routing, video ID expansion

- _cleanup_track: never delete files from kept directory (data/music/)
  even when track.keep=False -- fixes kept files vanishing on replay
- !kept rm: skip to next track if removing the currently playing one
- !skip: silent (no reply), restarts play loop for autoplay on empty queue
- TTS plays through merlin's own connection instead of derp's, preventing
  choppy audio when music and TTS compete for the same output buffer
- !play recognizes bare YouTube video IDs (11-char alphanumeric)
- !kept rm <id> subcommand for removing individual kept tracks

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

plugins/music.py

@@ -79,6 +79,16 @@ def _truncate(text: str, max_len: int = _MAX_TITLE_LEN) -> str:
     return text[: max_len - 3].rstrip() + "..."
 
 
+_YT_VIDEO_ID_RE = re.compile(r"^[A-Za-z0-9_-]{11}$")
+
+
+def _expand_video_id(text: str) -> str:
+    """Expand a bare YouTube video ID to a full URL."""
+    if _YT_VIDEO_ID_RE.match(text):
+        return f"https://www.youtube.com/watch?v={text}"
+    return text
+
+
 def _is_url(text: str) -> bool:
     """Check if text looks like a URL rather than a search query."""
     return text.startswith(("http://", "https://", "ytsearch:"))
@@ -309,9 +319,13 @@ def _download_track(url: str, track_id: str, title: str = "") -> Path | None:
 
 
 def _cleanup_track(track: _Track) -> None:
-    """Delete the local audio file unless marked to keep."""
+    """Delete the local audio file unless marked to keep or in kept dir."""
     if track.local_path is None or track.keep:
         return
+    # Never delete files from the kept directory -- they may have been
+    # reused by _download_track for a non-kept playback of the same URL.
+    if track.local_path.parent == _MUSIC_DIR:
+        return
     try:
         track.local_path.unlink(missing_ok=True)
         log.info("music: deleted %s", track.local_path.name)
@@ -844,6 +858,9 @@ async def cmd_play(bot, message):
         _ensure_loop(bot)
         return
 
+    # Expand bare YouTube video IDs (e.g. "U1yQMjFZ6j4")
+    url = _expand_video_id(url)
+
     # Strip #random fragment before URL classification / resolution
     shuffle = False
     if _is_url(url) and url.endswith("#random"):
@@ -1074,14 +1091,7 @@ async def cmd_skip(bot, message):
 
     await _fade_and_cancel(bot)
 
-    if ps["queue"]:
-        _ensure_loop(bot)
-        await bot.reply(
-            message,
-            f"Skipped: {_truncate(skipped.title)}",
-        )
-    else:
-        await bot.reply(message, "Skipped, queue empty")
+    _ensure_loop(bot)
 
 
 @command("prev", help="Music: !prev -- play previous track")
@@ -1475,14 +1485,15 @@ async def cmd_keep(bot, message):
     await bot.reply(message, f"Keeping #{keep_id}: {label}")
 
 
-@command("kept", help="Music: !kept [clear|repair] -- list, clear, or repair kept files")
+@command("kept", help="Music: !kept [rm <id>|clear|repair] -- manage kept files")
 async def cmd_kept(bot, message):
-    """List, clear, or repair kept audio files in data/music/.
+    """List, clear, remove, or repair kept audio files in data/music/.
 
     Usage:
-        !kept           List kept tracks with metadata and file status
-        !kept clear     Delete all kept files and metadata
-        !kept repair    Re-download kept tracks whose local files are missing
+        !kept              List kept tracks with metadata and file status
+        !kept rm <id>      Remove a single kept track by ID
+        !kept clear        Delete all kept files and metadata
+        !kept repair       Re-download kept tracks whose local files are missing
     """
     if not _is_mumble(bot):
         await bot.reply(message, "Mumble-only feature")
@@ -1491,6 +1502,34 @@ async def cmd_kept(bot, message):
     parts = message.text.split()
     sub = parts[1].lower() if len(parts) >= 2 else ""
 
+    if sub == "rm":
+        if len(parts) < 3:
+            await bot.reply(message, "Usage: !kept rm <id>")
+            return
+        kid = parts[2].lstrip("#")
+        raw = bot.state.get("music", f"keep:{kid}")
+        if not raw:
+            await bot.reply(message, f"No kept track with ID #{kid}")
+            return
+        try:
+            meta = json.loads(raw)
+        except (json.JSONDecodeError, TypeError):
+            meta = {}
+        filename = meta.get("filename", "")
+        if filename:
+            fpath = _MUSIC_DIR / filename
+            fpath.unlink(missing_ok=True)
+        bot.state.delete("music", f"keep:{kid}")
+        title = meta.get("title") or filename or kid
+        await bot.reply(message, f"Removed #{kid}: {_truncate(title)}")
+        # Skip if this track is currently playing
+        ps = _ps(bot)
+        cur = ps.get("current")
+        if cur and filename and cur.local_path and cur.local_path.name == filename:
+            await _fade_and_cancel(bot)
+            _ensure_loop(bot)
+        return
+
     if sub == "clear":
         count = 0
         if _MUSIC_DIR.is_dir():