diigo-cache: invalidate the last N days of cached pages

invalidateRecent(days) drops the cached pages holding anything diigo
updated within the last N days (on the cache's injected clock), and
every page before them, so the next read or fill refetches them; item
rows stay. Exposed on the fill capability (private and public) and on
the webkey page as "invalidate the last N days" per cache.

A user-requested refetch, not a change in what stored state means.

Generated-by: Claude Opus 5.5

diigo-cache/tests/caches.test.ts

@@ -159,6 +159,30 @@ describe("page numbering (schema v2)", () => {
 	});
 });
 
+describe("invalidateRecent", () => {
+	it("drops the pages holding anything updated in the last N days, and only those", async () => {
+		const stub = testEnv.CACHE_DO.get(testEnv.CACHE_DO.newUniqueId());
+		// deep_dee: one bookmark a day, newest first; page 1 = days 0–99,
+		// page 2 = days 100–199, page 3 = days 200–299
+		await stub.setup({ webappId: "fake-deep-webapp" });
+		for (const n of [1, 2, 3]) await stub.page(n, PAGE_SIZE);
+		expect(await stub.invalidateRecent(150)).toEqual({ pages: 2 });
+		expect((await stub.page(3, PAGE_SIZE)).cached).toBe(true);
+		expect((await stub.page(2, PAGE_SIZE)).cached).toBe(false);
+		expect((await stub.page(1, PAGE_SIZE)).cached).toBe(false);
+	});
+
+	it("drops nothing when nothing cached is that recent, and refuses a bad day count", async () => {
+		const stub = testEnv.CACHE_DO.get(testEnv.CACHE_DO.newUniqueId());
+		await stub.setup({ webappId: WEBAPP_ID }); // the plain account's dates are in 2023
+		await stub.page(1, PAGE_SIZE);
+		expect(await stub.invalidateRecent(7)).toEqual({ pages: 0 });
+		expect((await stub.page(1, PAGE_SIZE)).cached).toBe(true);
+		const refused = await stub.invalidateRecent(0).then(() => "", (e: unknown) => String(e));
+		expect(refused).toMatch(/days/);
+	});
+});
+
 describe("eviction", () => {
 	it("a cache miss leaves no undisposed RPC stubs to block eviction", async () => {
 		const stub = testEnv.CACHE_DO.get(testEnv.CACHE_DO.newUniqueId());