feat: repo foundation and course tooling

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

tools/test/sync-check.test.mjs

@@ -0,0 +1,16 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { run, fixtures } from "./helpers.mjs";
+import { join } from "node:path";
+
+test("sync_detects_missing_ts_test", () => {
+  const r = run("sync-check.mjs", [], { COURSE_ROOT: join(fixtures, "course-bad") });
+  assert.equal(r.code, 1);
+  assert.match(r.out, /test_01_a/);
+  assert.match(r.out, /test_01_b/);
+});
+
+test("sync_passes_consistent_course", () => {
+  const r = run("sync-check.mjs", [], { COURSE_ROOT: join(fixtures, "course") });
+  assert.equal(r.code, 0, r.out);
+});