fix: clean up test case directories after each test instead of at end

Moves case directory cleanup from afterAll to afterEach in all test
files that create cases. Previously, if the test suite was interrupted
or afterAll timed out, all case directories were left behind. Now each
test cleans up immediately after itself.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

test/quick-start.test.ts

@@ -18,16 +18,20 @@ describe('Quick Start API', () => {
     baseUrl = `http://localhost:${TEST_PORT}`;
   });
 
-  afterAll(async () => {
-    await server.stop();
-    // Cleanup created test cases
-    for (const caseName of createdCases) {
+  afterEach(() => {
+    // Clean up cases created during this test
+    while (createdCases.length > 0) {
+      const caseName = createdCases.pop()!;
       const casePath = join(CASES_DIR, caseName);
       if (existsSync(casePath)) {
         rmSync(casePath, { recursive: true, force: true });
       }
     }
-  }, 30000); // Increase timeout since server.stop() kills screen sessions
+  });
+
+  afterAll(async () => {
+    await server.stop();
+  }, 30000);
 
   describe('POST /api/quick-start', () => {
     it('should create default testcase and start interactive session', async () => {