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

compare-export.ts: the manual is a HELP string at the top of the module
(a docstring, as a value) and main prints it on bad usage. No reading
its own source, no regex, one copy; @file points at it.

Generated-by: Claude Opus 5.5

diigo-cache/scripts/compare-export.ts

@@ -1,14 +1,15 @@
 #!/usr/bin/env node
-/**
- * @file program script: does a cache hold everything in a diigo RSS export?
- *
- *     node scripts/compare-export.ts <cache.sqlite> <export.xml> <out-dir>
- *
- * Generates RSS from the cache's items (src/rss.ts) and compares it with
- * the export, keyed on link: title, tags, description, highlights and
- * sticky notes. Prints counts to stdout; writes <out-dir>/from-cache.rss
- * and <out-dir>/report.json (mismatched links, by category).
- */
+/** @file program script: does a cache hold everything in a diigo RSS export? See {@link HELP}. */
+
+/** the manual (a docstring, as a value): printed on bad usage */
+const HELP = `usage: node scripts/compare-export.ts <cache.sqlite> <export.xml> <out-dir>
+
+Generates RSS from the cache's items (src/rss.ts) and compares it with the
+export, keyed on link: title, tags, description, highlights and sticky
+notes. Prints counts to stdout; writes <out-dir>/from-cache.rss and
+<out-dir>/report.json (mismatched links, by category).
+`;
+
 import * as nodeFs from "node:fs/promises";
 import { basename, join } from "node:path";
 import { DatabaseSync } from "node:sqlite";
@@ -146,10 +147,7 @@ export async function main(
 ): Promise<void> {
 	const [dbPath, exportPath, outPath] = argv;
 	if (!dbPath || !exportPath || !outPath) {
-		// the @file comment is the manual: its indented synopsis line is the usage
-		const source = await fs.readFile(import.meta.filename, "utf8");
-		const synopsis = source.match(/^ \* +(node \S+\.ts .*)$/m)?.[1] ?? "see the @file comment";
-		stderr.write(`usage: ${synopsis}\n`);
+		stderr.write(HELP);
 		return exit(BAD_USAGE);
 	}
 	const cache = cacheItems(connect(dbPath));