Wire watch history, resume positions and persistent queue

WatchPage now records every played video in watch_history, saves the
playback position every 5 seconds and on stop/end (completed at >=95%),
and seeks back on replay when player.resume is "auto" - resume kicks in
between 30 seconds and 95% of the duration. The play queue persists
across restarts and reorders/removals write through immediately; the
main window's closeEvent flushes position and queue and releases libmpv.

PlayerPanel gains an automatic stall-retry: YouTube's CDN intermittently
serves stalled streams to non-browser clients (reproduced ~1/3 of
attempts headless with identical code), and a reload re-resolves onto a
healthy node - two retries after 25s of no playback, then a user-facing
error.

ytsage_constants now prepends the managed-binaries dir to PATH so
yt-dlp subprocesses (including mpv's ytdl_hook) can find the managed
Deno runtime - previously nothing exported APP_BIN_DIR, so the deno
integration silently never worked.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

ytsage/gui/ytsage_gui_main.py

@@ -1250,6 +1250,13 @@ class YTSageApp(QMainWindow, FormatTableMixin, VideoInfoMixin, AnalysisMixin):
     def closeEvent(self, event) -> None:
         """Handle application close event to ensure proper cleanup of background threads."""
         try:
+            # Persist watch position/queue and release libmpv
+            if hasattr(self, "watch_page"):
+                try:
+                    self.watch_page.shutdown()
+                except Exception as e:
+                    logger.debug(f"Watch page shutdown error: {e}")
+
             # Stop the analysis thread if it's running
             if hasattr(self, "_analysis_thread") and self._analysis_thread is not None and self._analysis_thread.isRunning():
                 logger.info("Stopping analysis thread...")