feat(codes): redeemed and expired codes move below, and new codes are marked

A game's Codes tab lists the codes still to use first; a code redeemed on
every server played, or past its stated expiry, is greyed in a "Redeemed or
expired" section below. A date-only expiry passes once that date has ended
everywhere. Settings → Your games marks a followed game with its count of
unseen, still usable codes until its Codes tab is opened.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

test/reader-codes-state.test.ts

@@ -0,0 +1,71 @@
+import { expect, test } from "bun:test";
+import type { CodesFeed, RedeemCode } from "../src/shared/codes.ts";
+import {
+  codeExpired,
+  codeUsed,
+  unseenUsableCodes,
+} from "../src/client/state/reader/codes.ts";
+
+const code = (id: string, over: Partial<RedeemCode> = {}): RedeemCode => ({
+  id,
+  game: "genshin",
+  code: id.toUpperCase(),
+  reward: null,
+  expiresAt: null,
+  expiresOn: null,
+  firstObservedAt: "2026-10-01T00:00:00.000Z",
+  sourceUrl: "https://example.com/codes",
+  ...over,
+});
+const now = Date.parse("2026-10-18T12:00:00.000Z");
+
+test("a code expires at its stated instant", () => {
+  expect(
+    codeExpired(code("a", { expiresAt: "2026-10-18T11:59:59.000Z" }), now),
+  ).toBe(true);
+  expect(
+    codeExpired(code("a", { expiresAt: "2026-10-18T12:00:01.000Z" }), now),
+  ).toBe(false);
+  expect(codeExpired(code("a"), now)).toBe(false);
+});
+
+test("a date-only expiry passes only once the date has ended everywhere", () => {
+  // 17 Oct has ended everywhere by 18 Oct 12:00 UTC; 18 Oct has not.
+  expect(codeExpired(code("a", { expiresOn: "2026-10-17" }), now)).toBe(true);
+  expect(codeExpired(code("a", { expiresOn: "2026-10-18" }), now)).toBe(false);
+  expect(codeExpired(code("a", { expiresOn: "2026-10-17" }), now - 1)).toBe(
+    false,
+  );
+});
+
+test("a code is used once it is redeemed on every server played", () => {
+  const redeemed = { "account:eu": { a: "2026-10-18T00:00:00.000Z" } };
+  expect(codeUsed(code("a"), ["account:eu"], redeemed)).toBe(true);
+  expect(codeUsed(code("a"), ["account:eu", "account:na"], redeemed)).toBe(
+    false,
+  );
+  expect(codeUsed(code("a"), [], redeemed)).toBe(false);
+});
+
+test("the Settings marker counts unseen codes that can still be used", () => {
+  const feed: CodesFeed = {
+    schemaVersion: 1,
+    sources: [],
+    codes: [
+      code("seen"),
+      code("fresh"),
+      code("expired", { expiresAt: "2026-10-01T00:00:00.000Z" }),
+      code("used"),
+      code("other", { game: "hsr" }),
+    ],
+  };
+  const ids = unseenUsableCodes(
+    feed,
+    ["seen"],
+    "genshin",
+    ["account:eu"],
+    { "account:eu": { used: "2026-10-18T00:00:00.000Z" } },
+    now,
+  ).map((c) => c.id);
+  expect(ids).toEqual(["fresh"]);
+});