fix(audio): prevent boosted clip jump-ahead on media load callback

Co-authored-by: kangjoseph90 <83045825+kangjoseph90@users.noreply.github.com>
Agent-Logs-Url: https://github.com/kangjoseph90/PictureBookBuilder/sessions/8cc21f7a-647b-4909-81d7-554a9fac6f42

Author: Copilot

src/ui/audio_mixer.py

@@ -501,8 +501,11 @@ def on_media_status_changed(status):
                         if status == QMediaPlayer.MediaStatus.LoadedMedia:
                             player.setPlaybackRate(self._playback_rate)
                             if self._playing:
-                                current_tic = self._position - clip.timeline_start
-                                corrected_pos = int(max(0.0, current_tic * seek_correction) * 1000)
+                                # Use the originally scheduled position instead of recalculating
+                                # from self._position. Boosted path can spend noticeable time in
+                                # ffmpeg extraction, and using current timeline position here can
+                                # skip into the clip unexpectedly when entering it.
+                                corrected_pos = int(max(0.0, time_into_clip * seek_correction) * 1000)
                                 player.setPosition(corrected_pos)
                                 player.play()
                             else: