fix: final review — cached links keep their expiry; history removal sticks; saves flushed

- A link reused from the rehost cache keeps the expiry it was uploaded with, and
  links near expiry are uploaded again (a dead litterbox link could be filed).
- History saving moves into HistoryKeeper (tested): removing an entry or clearing
  the history cancels a pending save and stops tracking the series on screen;
  a pending edit is saved before a new search, before opening another entry and
  when the page is hidden; opening an entry no longer re-saves the current one.
- The "couldn't be saved" line sits outside the History list, so it shows even
  when the list is empty; a refused IndexedDB says history is off.
- Recently searched bands wrap their meta line instead of cutting the count.

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

test/session.test.ts

@@ -1,4 +1,4 @@
-import { describe, expect, test } from "bun:test";
+import { describe, expect, setSystemTime, test } from "bun:test";
 import { HostError } from "../src/core/hosting/host";
 import { MangaBakaError } from "../src/core/mangabaka/client";
 import type { SubmissionImage } from "../src/core/mangabaka/types";
@@ -186,3 +186,44 @@ describe("hosting is remembered on the cards", () => {
     expect(second.cards[0]!.hostedUrl).toBe("https://litter.catbox.moe/a.jpg");
   });
 });
+
+describe("hosted links that expire", () => {
+  const T = Date.UTC(2026, 9, 15, 10);
+  const MIN = 60_000;
+
+  test("a link reused from the rehost cache keeps its original expiry", async () => {
+    const fake = new FakeTransport().on(LITTERBOX, () => text("https://litter.catbox.moe/a.jpg"));
+    const s = new Session(deps(fake));
+    s.load(result());
+    try {
+      setSystemTime(new Date(T));
+      await s.rehost("litterbox", { litterboxTime: "1h" });
+      setSystemTime(new Date(T + 20 * MIN));
+      await s.rehost("litterbox", { litterboxTime: "1h" });
+      expect(s.cards[0]!.hosting!.until).toBe(T + 60 * MIN);
+    } finally {
+      setSystemTime();
+    }
+  });
+
+  test("a restored link that has expired since is uploaded again, not reused", async () => {
+    let n = 0;
+    const fake = new FakeTransport().on(LITTERBOX, () => text(`https://litter.catbox.moe/${++n}.jpg`));
+    const r = result();
+    const first = new Session(deps(fake));
+    first.load(r);
+    try {
+      setSystemTime(new Date(T));
+      await first.rehost("litterbox", { litterboxTime: "1h" });
+      setSystemTime(new Date(T + 55 * MIN));
+      const second = new Session(deps(fake));
+      second.restore(r, first.cards.map((c) => ({ ...c })), true, null);
+      setSystemTime(new Date(T + 90 * MIN));
+      await second.rehost("litterbox", { litterboxTime: "1h" });
+      expect(second.cards[0]!.hostedUrl).toBe("https://litter.catbox.moe/2.jpg");
+      expect(second.cards[0]!.hosting!.until).toBe(T + 150 * MIN);
+    } finally {
+      setSystemTime();
+    }
+  });
+});