fix(filters): the year dialog fits a tablet, walks by arrow keys, names one year once

- a decade cell is a 36-high box with its count under the year (owner A)
- arrow keys walk the cells: along a decade, then to the nearest year below
- clearing the kept older year hands the focus on instead of dropping it
- More... shows while a year with titles is hidden, as a plain chip
- the decade caption is not read twice; the Plex range fields have names
- one Plex year is labelled 1999, not 1999-1999, via oneYear/singleYear
- tests for the Plex wiring and the feed year clearing the upload date

frontend/src/lib/api.ts

@@ -52,6 +52,8 @@ import { plexApi } from "./api/plex";
 export type * from "./api/plex";
 export {
   EMPTY_PLEX_FILTERS,
+  oneYear,
+  singleYear,
   plexFilterCount,
   coercePlexFilters,
   plexFiltersSignature,

frontend/src/lib/api/plex.ts

@@ -261,6 +261,17 @@ export interface PlexPersonDetail {
   movies: PlexCard[]; // enabled-library movies whose cast OR directors include this person
   shows: PlexCard[]; // enabled-library shows, same
 }
+/** One year as a Plex filter: a range of one, both ends set (the year picker, a year on an info page).
+ *  `null` clears it. */
+export const oneYear = (year?: number | null): Pick<PlexFilters, "yearMin" | "yearMax"> => ({
+  yearMin: year ?? null,
+  yearMax: year ?? null,
+});
+
+/** The one year a filter narrows to, when its range is a single year. */
+export const singleYear = (f: Pick<PlexFilters, "yearMin" | "yearMax">): number | undefined =>
+  f.yearMin != null && f.yearMin === f.yearMax ? f.yearMin : undefined;
+
 // The expanded Plex browse filters (movie libraries). Persisted per-account as JSON.
 export interface PlexFilters {
   genres: string[];

frontend/src/lib/plexActiveFilters.dom.test.ts

@@ -0,0 +1,26 @@
+// @vitest-environment jsdom
+import { describe, it, expect } from "vitest";
+import { buildPlexActiveFilters } from "./plexActiveFilters";
+import { EMPTY_PLEX_FILTERS, type PlexFilters } from "./api";
+
+const t = (key: string) => key;
+const yearLabel = (f: Partial<PlexFilters>) =>
+  buildPlexActiveFilters(
+    { ...EMPTY_PLEX_FILTERS, ...f },
+    "",
+    () => {},
+    () => {},
+    t,
+  ).find((c) => c.key === "year")?.label;
+
+describe("the Plex year chip", () => {
+  it("names one year as the year, not a range of one", () => {
+    expect(yearLabel({ yearMin: 1999, yearMax: 1999 })).toBe("plex.filter.year: 1999");
+  });
+
+  it("names a range and an open end as before", () => {
+    expect(yearLabel({ yearMin: 1990, yearMax: 1999 })).toBe("plex.filter.year: 1990–1999");
+    expect(yearLabel({ yearMin: 1990 })).toBe("plex.filter.year: ≥1990");
+    expect(yearLabel({ yearMax: 1999 })).toBe("plex.filter.year: ≤1999");
+  });
+});

frontend/src/lib/plexActiveFilters.ts

@@ -1,6 +1,6 @@
 import { vocabI18nKey } from "./vocab";
 import { type ActiveFilter } from "./useActiveFilters";
-import { type PlexFilters } from "./api";
+import { singleYear, type PlexFilters } from "./api";
 
 type TFn = (key: string, options?: Record<string, unknown>) => string;
 
@@ -42,12 +42,15 @@ export function buildPlexActiveFilters(
     });
   }
   if (has(filters.yearMin) || has(filters.yearMax)) {
+    const one = singleYear(filters);
     const range =
-      has(filters.yearMin) && has(filters.yearMax)
-        ? `${filters.yearMin}–${filters.yearMax}`
-        : has(filters.yearMin)
-          ? `≥${filters.yearMin}`
-          : `≤${filters.yearMax}`;
+      one != null
+        ? String(one)
+        : has(filters.yearMin) && has(filters.yearMax)
+          ? `${filters.yearMin}–${filters.yearMax}`
+          : has(filters.yearMin)
+            ? `≥${filters.yearMin}`
+            : `≤${filters.yearMax}`;
     out.push({
       key: "year",
       label: `${t("plex.filter.year")}: ${range}`,