diigo-cache: bookmark cache in Durable Objects (goal 1c)

The dump worker becomes a page cache: a hit is served from DO SQLite
storage with no diigo call; a miss asks the webapp instance in the
cache's wiring and etches the page.

- two independent caches, one behavior (PagedCache): DiigoCache keeps
  every item; PublicCache keeps shared items only, dropping private
  rows before they are stored; served at /public/<username> (HTML page
  form, or JSON)
- create flow on one port: /_connect relays webapp's mint form, /_mint
  proxies the mint, /_wire wires a private or public cache; /_publish
  adds a public cache later
- ids are webkeys: kept out of URLs (POST bodies), shown and logged
  only as a hash fingerprint; saved to the password manager under the
  holder's petname (never sent to the server)
- items keyed on diigo's link_id; username from u_name; unkeyable
  items and every failure path are logged; each page read logs hit/miss
- tests run the real worker + DOs in the vitest pool against a fake
  webapp (tests/fake-webapp.js)

Generated-by: opencode (GLM)
Generated-by: Claude Opus 5.5

diigo-cache/tests/fake-webapp.js

@@ -0,0 +1,72 @@
+/**
+ * @file a stand-in for webapp's `WebAppFactory` entrypoint, for tests: an
+ * auxiliary worker (plain JS — the vitest pool doesn't transform aux
+ * workers) serving diigo-shaped `load_user_items` pages. 30 items, every
+ * third private; one webapp id is known. Counts its diigo calls so tests
+ * can tell a cache hit (no call) from a miss.
+ */
+import { RpcTarget, WorkerEntrypoint } from "cloudflare:workers";
+
+const KNOWN_WEBAPP = "fake-webapp-id";
+const TOTAL = 30;
+
+/** item n (1-based, updated-desc order): diigo's field names, made-up values */
+function item(n) {
+	return {
+		link_id: 1000 + n,
+		url: `https://example.com/${n}`,
+		title: `bookmark ${n}`,
+		description: "",
+		private: n % 3 === 0,
+		u_name: "alice_99",
+		first_by: "someone-else",
+		user_id: 4242,
+		tags: "",
+		created_at: 1700000000,
+		updated_at: 1700001000 - n,
+	};
+}
+
+let calls = 0;
+
+class FakeGet extends RpcTarget {
+	#path;
+	#params;
+	constructor(path, params) {
+		super();
+		this.#path = path;
+		this.#params = params;
+	}
+	pathjoin(ref) {
+		return new FakeGet(ref, this.#params);
+	}
+	query(params) {
+		return new FakeGet(this.#path, { ...this.#params, ...params });
+	}
+	async get() {
+		calls += 1;
+		if (this.#path !== "load_user_items") throw new Error(`fake webapp: no route ${this.#path}`);
+		const count = Number(this.#params.count);
+		const page = Number(this.#params.page_num);
+		const items = [];
+		for (let n = (page - 1) * count + 1; n <= Math.min(page * count, TOTAL); n += 1) items.push(item(n));
+		return JSON.stringify({ total: TOTAL, items });
+	}
+}
+
+export class WebAppFactory extends WorkerEntrypoint {
+	async at(id) {
+		if (id !== KNOWN_WEBAPP) throw new Error("fake webapp: unknown id");
+		return new FakeGet("", {});
+	}
+	/** how many diigo calls so far (test hook) */
+	async calls() {
+		return calls;
+	}
+}
+
+export default {
+	fetch() {
+		return new Response("fake webapp", { status: 404 });
+	},
+};