fix(player): only the credits that end an item move on to the next one

An item can carry several credits blocks with mid- and post-credit scenes between
them, and Plex flags the one that really ends it. The player left at the first
block. Now the Plex-final block moves on (by the auto-skip or the Skip button), an
earlier block is only skipped to its end by the button, and with no final flag the
last block ends the item by the button alone.

backend/tests/test_plex_detail.py

@@ -401,3 +401,38 @@ def test_item_detail_names_tracks_from_their_language_not_plexs_title(
         ("magyar Forced", "hu", True, False, None),
         ("English SDH", "en", False, True, None),
     ]
+
+
+def test_item_detail_markers_carry_plex_final_flag(db, monkeypatch, override_dep):
+    """An item can carry several credits markers — mid- and post-credit scenes sit between them —
+    and only the one Plex flags `final` is the real end; the player needs that flag to know which
+    credits may move on to the next item."""
+    lib = PlexLibrary(plex_key="1", title="Movies", kind="movie", enabled=True)
+    db.add(lib)
+    db.flush()
+    db.add(PlexItem(rating_key="m2", library_id=lib.id, kind="movie", title="Iron Man"))
+    db.commit()
+    user = _user(db, "markers@example.com")
+    db.commit()
+
+    meta = {
+        "Marker": [
+            {"type": "intro", "startTimeOffset": 1000, "endTimeOffset": 60000},
+            {"type": "credits", "startTimeOffset": 6811000, "endTimeOffset": 6831000},
+            {
+                "type": "credits",
+                "startTimeOffset": 7549000,
+                "endTimeOffset": 7559000,
+                "final": True,
+            },
+            {"type": "commercial", "startTimeOffset": 1, "endTimeOffset": 2},
+        ]
+    }
+    monkeypatch.setattr(detail_routes, "PlexClient", lambda db: _StubClient(meta))
+    resp = _get(db, user, monkeypatch, override_dep, "/api/plex/item/m2")
+    assert resp.status_code == 200, resp.text
+    assert resp.json()["markers"] == [
+        {"type": "intro", "start_s": 1.0, "end_s": 60.0, "final": False},
+        {"type": "credits", "start_s": 6811.0, "end_s": 6831.0, "final": False},
+        {"type": "credits", "start_s": 7549.0, "end_s": 7559.0, "final": True},
+    ]