feat(codes): mark a code dead once the owner confirms it in game

Game8 still lists Y1INABQB6DEX, 2BJ64QRZ7RT8 and PLDXIB886Y1S as active
Genshin codes after the game refused them. CODE_CHECKS records the
owner's in-game check; build-codes stamps the matching code confirmedDead,
and the Codes tab shows it expired: "Confirmed expired in game, 2026-10-20."

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

test/reader-codes-state.test.ts

@@ -69,3 +69,18 @@ test("the Settings marker counts unseen codes that can still be used", () => {
   ).map((c) => c.id);
   expect(ids).toEqual(["fresh"]);
 });
+
+test("a code the owner confirmed dead is expired whatever its stated expiry", () => {
+  expect(codeExpired(code("a", { confirmedDead: "2026-10-20" }), now)).toBe(
+    true,
+  );
+  expect(
+    codeExpired(
+      code("a", {
+        confirmedDead: "2026-10-20",
+        expiresAt: "2026-12-01T00:00:00.000Z",
+      }),
+      now,
+    ),
+  ).toBe(true);
+});