diigo-cache: public list shows each bookmark's date first

The list is in diigo's updated order; each item now leads with its
updated_at as Date#toISOString() (diigo sends epoch seconds; updatedISO
converts, tested), or "(no date)".

Generated-by: Claude Opus 5.5

diigo-cache/tests/caches.test.ts

@@ -117,6 +117,8 @@ describe("worker routes", () => {
 		const again = await (await call(`/public/${username}?page=2`)).text();
 		expect(again).toContain("<strong>cache: HIT");
 		expect(html).toContain("bookmark 25");
+		// the date comes first, in toISOString() form
+		expect(html).toMatch(/<li><time datetime="\d{4}-\d\d-\d\dT[\d:.]+Z">[^<]+<\/time> <a /);
 		expect(html).not.toContain("bookmark 27"); // private (27 % 3 === 0)
 
 		const json = (await (

diigo-cache/tests/items.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from "vitest";
-import { publicOnly, toRows, usernameOf } from "../src/items.js";
+import { publicOnly, toRows, updatedISO, usernameOf } from "../src/items.js";
 import type { Item } from "../src/items.js";
 
 /** a load_user_items row: diigo's actual field names (observed
@@ -70,3 +70,14 @@ describe("publicOnly", () => {
 		expect(JSON.stringify(rows)).not.toContain("secret.example");
 	});
 });
+
+describe("updatedISO", () => {
+	it("reads diigo's updated_at as epoch seconds", () => {
+		expect(updatedISO({ updated_at: 1700000000 })).toBe("2023-11-14T22:13:20.000Z");
+	});
+
+	it("answers empty when there is no usable date", () => {
+		expect(updatedISO({})).toBe("");
+		expect(updatedISO({ updated_at: "yesterday" })).toBe("");
+	});
+});