diigo-cache: RSS in diigo's export shape, from cached items

src/rss.ts renders items as RSS 2.0 in the shape of diigo's RSS export:
title, link, and a description packing Tags:…;Description:…;
Annotations and Sticky notes:… (Highlight:/Sticky notes: lines). Unlike
the export it is well-formed (characters XML forbids are dropped; the
export carries some raw) and keeps whole titles (the export cuts at
255). Pure: dates come from the caller.

scripts/compare-export.ts (a program script: node, node:sqlite) loads a
cache's items, writes the RSS, and compares it with an export, keyed on
link, reporting counts by category.

Generated-by: Claude Opus 5.5

diigo-cache/tests/rss.test.ts

@@ -0,0 +1,50 @@
+import { describe, expect, it } from "vitest";
+import { itemDescription, rssItem, toRss } from "../src/rss.js";
+
+// shaped like diigo's export (field layout observed 2026-10-07), made-up values
+
+describe("itemDescription", () => {
+	it("packs tags, description, and annotations the way diigo's export does", () => {
+		expect(
+			itemDescription({
+				tags: "ocap,js",
+				description: "a note",
+				annotations: [
+					{ content: "first highlight", stickyNotes: [] },
+					{ content: "second", stickyNotes: [{ content: "a sticky\n\nwith lines" }, { content: "another" }] },
+				],
+			}),
+		).toBe(
+			"Tags:ocap,js;Description:a note;Annotations and Sticky notes:" +
+				"Highlight:first highlight\n" +
+				"Highlight:second\nSticky notes:a sticky\n\nwith lines\nSticky notes:another\n",
+		);
+	});
+
+	it("says no_tag when there are no tags, and leaves empty parts empty", () => {
+		expect(itemDescription({ tags: "", description: "", annotations: [] })).toBe(
+			"Tags:no_tag;Description:;Annotations and Sticky notes:",
+		);
+	});
+});
+
+describe("rssItem / toRss", () => {
+	it("is well-formed even when diigo's text isn't: forbidden characters dropped, ]]> split", () => {
+		const xml = rssItem({ title: "bad\u0003char", url: "https://a.example/", tags: "", description: "x]]>y" });
+		expect(xml).not.toContain("\u0003");
+		expect(xml).toContain("<title><![CDATA[badchar]]></title>");
+		expect(xml).toContain("Description:x]]]]><![CDATA[>y;");
+	});
+
+	it("keeps the whole title (diigo's export cuts at 255)", () => {
+		const title = "t".repeat(300);
+		expect(rssItem({ title, url: "u" })).toContain(title);
+	});
+
+	it("wraps items in an RSS 2.0 channel, dated by the caller", () => {
+		const feed = toRss([{ title: "a", url: "u" }], { title: "my items", pubDate: "Wed, 07 Oct 2026 12:00:00 +0000" });
+		expect(feed).toMatch(/^<\?xml version="1.0"\?>\n<rss version="2.0">\n<channel>/);
+		expect(feed).toContain("<pubDate>Wed, 07 Oct 2026 12:00:00 +0000</pubDate>");
+		expect(feed).toContain("<item><title><![CDATA[a]]></title>");
+	});
+});