fix(plex): a refused finish restores no resume point at the media's own end

The rollback of a refused watched mark guarded against Plex's REPORTED
duration. On a file shorter than its metadata the end sits outside the
finish margin, so playing to the end and having the mark refused stored the
very end as a resume point on an unwatched row: a ~99% bar that reopened in
the last seconds. The media's own ended flag now decides.

frontend/src/lib/plexPlayerHooks.ts

@@ -215,6 +215,10 @@ export function usePlexProgress(opts: {
       // Watched badge the server disagreed with (round 5).
       const pos = Math.floor(absRef.current);
       const dur = durationRef.current;
+      // The media's own end, not Plex's reported duration: a file shorter than its metadata (a
+      // configuration this file documents) ends outside the margin below, and restoring THAT
+      // position left an unwatched item with a ~99% bar that reopened in its last seconds.
+      const ended = video?.ended === true;
       void confirmed?.catch(() => {
         finishRefused = true;
         // Restore the resume point the finish replaced — but ONLY where there is one to restore.
@@ -224,7 +228,7 @@ export function usePlexProgress(opts: {
         // performed, through a second route, exactly the write that had just been refused — while
         // the caller's error toast was already on screen saying it had failed (round 6). The
         // credits-skip caller captures a mid-episode position and is unaffected.
-        if (pos > 0 && dur > 0 && pos <= dur - FINISH_MARGIN_S)
+        if (!ended && pos > 0 && dur > 0 && pos <= dur - FINISH_MARGIN_S)
           api.plexProgress(id, pos, dur, true).catch(() => {});
         // `settle` may already have patched the detail to watched / 0 on the way out. Dropping that
         // entry rather than invalidating it: an invalidated query with no observer keeps serving its