Bridge: extend mpd:state with nextTitles[] for queue peek

Adds nextTitles (array of up to 3 display strings) plus mirrored single
nextTitle/nextArtist/nextTrackTitle/nextFile for the immediate next
track. Drives the Music Box overlays' 3-up "coming next" lines without
overlays needing to query MPD themselves.

Reads MPD status.nextsong, walks playlistinfo for the next 3 indices,
applies the existing _flatten_tag + display-string cascade. Fields are
None / [] at end of queue. Backwards-compatible: overlays that don't
read the new keys are unaffected.

bridges/mpd-state.py

@@ -9,7 +9,13 @@ the custom music/index.html browser daemon as the source of truth.
 
 Payload shape matches the original daemon's broadcastState() so the overlay
 needs zero changes:
-    { _type, index, total, title, file, currentTime, duration, paused }
+    { _type, index, total, title, file, currentTime, duration, paused,
+      nextTitle, nextArtist, nextTrackTitle, nextFile, nextTitles }
+Next-track fields are populated when MPD reports `nextsong` in its status.
+`nextTitles` is up to 3 display strings peeked from the queue starting at
+the current song's successor — used by the Music Box overlay to show
+"coming up" lines. The single `nextTitle`/`nextArtist`/etc. fields mirror
+nextTitles[0] for overlays that only need one.
 
 Reads OBS WS credentials from ../vendor/obs-config.js (auto-generated by
 scripts/setup.sh from plugin_config/obs-websocket/config.json — single source of truth).
@@ -74,18 +80,12 @@ def _flatten_tag(v):
     return v or None
 
 
-def mpd_to_event(status: dict, song: dict) -> dict:
-    """Translate `status` + `currentsong` into the overlay's expected payload.
-
-    Display string in `title` is built `Artist - Title` from ID3/Vorbis tags
-    when both are present, then degrades through tag-only → filename stem
-    (which is already "Artist - Title" for the NCS Directory naming convention)
-    → None. The separate `artist` field is emitted for future overlay uses
-    that want to style artist + title differently."""
-    paused   = status.get("state", "stop") != "play"
-    elapsed  = float(status.get("elapsed") or 0)
-    duration = float(status.get("duration") or song.get("duration") or 0)
+def _song_display(song: dict) -> tuple:
+    """Extract (display, artist, track_title) from an MPD song dict.
 
+    Display string is built `Artist - Title` from ID3/Vorbis tags when both
+    are present, then degrades through tag-only → filename stem (already
+    "Artist - Title" for the NCS Directory naming convention) → None."""
     artist     = _flatten_tag(song.get("artist") or song.get("albumartist"))
     track_name = _flatten_tag(song.get("title"))
 
@@ -98,6 +98,30 @@ def mpd_to_event(status: dict, song: dict) -> dict:
     else:
         display = None
 
+    return display, artist, track_name
+
+
+def mpd_to_event(status: dict, song: dict, next_songs: list | None = None) -> dict:
+    """Translate `status` + `currentsong` (+ optional `next_songs`, the next
+    up to 3 queued tracks) into the overlay payload. The single `nextTitle`
+    family mirrors `nextTitles[0]` for overlays that only need one."""
+    paused   = status.get("state", "stop") != "play"
+    elapsed  = float(status.get("elapsed") or 0)
+    duration = float(status.get("duration") or song.get("duration") or 0)
+
+    display, artist, track_name = _song_display(song)
+
+    next_titles = []
+    next_display, next_artist, next_track, next_file = None, None, None, None
+    if next_songs:
+        for ns in next_songs:
+            d, a, t = _song_display(ns)
+            if d is not None:
+                next_titles.append(d)
+        if next_songs[0]:
+            next_display, next_artist, next_track = _song_display(next_songs[0])
+            next_file = next_songs[0].get("file")
+
     return {
         "index":       int(status["song"]) if "song" in status else -1,
         "total":       int(status.get("playlistlength") or 0),
@@ -108,6 +132,11 @@ def mpd_to_event(status: dict, song: dict) -> dict:
         "currentTime": elapsed,
         "duration":    duration,
         "paused":      paused,
+        "nextTitle":   next_display,
+        "nextArtist":  next_artist,
+        "nextTrackTitle":   next_track,
+        "nextFile":    next_file,
+        "nextTitles":  next_titles,
     }
 
 
@@ -117,6 +146,8 @@ class SharedState:
             "index": -1, "total": 0,
             "title": None, "artist": None, "trackTitle": None, "file": None,
             "currentTime": 0, "duration": 0, "paused": True,
+            "nextTitle": None, "nextArtist": None, "nextTrackTitle": None, "nextFile": None,
+            "nextTitles": [],
         }
         self.changed = asyncio.Event()
 
@@ -134,7 +165,21 @@ async def mpd_loop(state: SharedState):
             while True:
                 status = await client.status()
                 song   = await client.currentsong()
-                state.data = mpd_to_event(status, song)
+                # Peek the next up-to-3 tracks. MPD's `nextsong` is the index
+                # of the immediate successor; we walk forward from there until
+                # we hit the queue end or 3 entries, whichever comes first.
+                next_songs = []
+                if "nextsong" in status:
+                    start = int(status["nextsong"])
+                    total = int(status.get("playlistlength") or 0)
+                    for i in range(start, min(start + 3, total)):
+                        try:
+                            rows = await client.playlistinfo(i)
+                            if rows:
+                                next_songs.append(rows[0])
+                        except Exception:
+                            break  # transient — let it retry next tick
+                state.data = mpd_to_event(status, song, next_songs)
                 state.changed.set()
                 await asyncio.sleep(TICK_SECONDS)
         except Exception as e: