feat(web): show the vanished flag on seasons

web/src/main.ts

@@ -2338,7 +2338,17 @@ function seriesMain(board: HTMLElement, tvDeck: TvReleasesView, views: HideableV
       });
     });
 
-    line.append(disclose, name, track, seasonCountsChip(season), space, searchBtn, deckBtn);
+    line.append(disclose, name, track, seasonCountsChip(season));
+    // The season-level twin of the episode flag above: gone upstream while
+    // files under it remained.
+    if (season.vanished) {
+      line.append(
+        chip("vanished", (span) => {
+          span.dataset.flag = "vanished";
+        }),
+      );
+    }
+    line.append(space, searchBtn, deckBtn);
     item.append(line);
 
     const episodes = document.createElement("ul");

web/src/series.ts

@@ -36,6 +36,8 @@ export interface ApiSeason {
   id: number;
   number: number;
   tracked: boolean;
+  /** Gone upstream while a file under it remained — a conflict, not a state. */
+  vanished: boolean;
   episodes: ApiEpisode[];
 }