fix: verify-references installs TS deps; sync-check covers expansion tests; template gitignore and passWithNoTests

verify-references ran a bare `npx vitest run` in the staged reference, which
fetched an unrelated vitest that could not load the reference config. It now
installs the reference's devDependencies first. sync-check also checks each
module's expansion/tests against ### headings in expansion/README.md.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tools/lib.mjs

@@ -39,9 +39,9 @@ export function testNames(path, lang) {
   return [...names].sort();
 }
 
-/** `### test_…` headings in a module's scenarios.md. */
-export function scenarioNames(path) {
-  const f = join(path, "scenarios.md");
+/** `### test_…` headings in a module's scenarios.md (or another file in `path`). */
+export function scenarioNames(path, file = "scenarios.md") {
+  const f = join(path, file);
   if (!existsSync(f)) return [];
   const names = new Set();
   for (const m of readFileSync(f, "utf8").matchAll(/^### (test_\w+)/gm)) names.add(m[1]);