Instead of play → pause → sleep → seek when restoring a paused session,
introduce loadTrackPaused which sets internal state and fires UI/OS
callbacks (song change, paused) without touching MPV. On Continue(),
detect pendingLoadPaused and start MPV playback from the saved position.
Also triggers waveform pre-generation for the paused track via the
onBeforeSongChange hook.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>