When QBZ becomes the active renderer (takeback), force a stream of the
current track and resume at the peer's position instead of failing or
restarting from 0:
- add QconnectRendererEngine::has_loaded_audio so the orchestration can
tell a stale track_id left by stop() from audio that is actually
buffered. stop() clears the buffer but leaves current_track_id, so the
track-id guard alone skipped the reload and the next resume hit
no audio data available.
- force_remote_track_stream on SetActive(true): reload even when the
track id matches (unless already streaming it), at the handed-off
position.
- thread the SetState position into ensure_remote_track_loaded so the
first takeback of a session (whose load lands in the SetState path)
also resumes at the peer's position rather than streaming from 0 and
issuing a forward seek the audio thread ignores past the watermark.
cc