When QBZ is CONTROLLING a peer renderer the local player is stopped, so
the poll loop saw track_id == 0 and the seek bar froze. Add
RemoteNowPlaying + SlintQconnectService::remote_now_playing(), sourced
from effective_remote_renderer_snapshot (peer position / updated_at /
playing). The poll loop now branches at the top of each tick: when a peer
is active it drives position/duration/progress/playing from the peer
(duration from the core queue's current track, position extrapolated and
clamped), resets the local edge trackers, and skips the local body. In
every non-controller situation remote_now_playing returns None and the
existing local path runs byte-unchanged, so renderer mode does not regress.
cc
vicrodh
6405b10204