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/test/fixtures/course-bad/01-a/expansion/README.md

@@ -0,0 +1 @@
+# Expansion

tools/test/fixtures/course-bad/01-a/expansion/tests/rust/c.rs

@@ -0,0 +1,2 @@
+#[test]
+fn test_01x_c() {}

tools/test/fixtures/course/01-m01/expansion/README.md

@@ -0,0 +1,3 @@
+# Expansion
+
+### test_01x_a

tools/test/fixtures/course/01-m01/expansion/tests/rust/m01x.rs

@@ -0,0 +1,2 @@
+#[test]
+fn test_01x_a() {}

tools/test/fixtures/course/01-m01/expansion/tests/ts/m01x.test.ts

@@ -0,0 +1,2 @@
+import { test } from "vitest";
+test("test_01x_a", () => {});