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/session-cleanup.test.ts

@@ -1,4 +1,4 @@
-import { describe, it, expect, beforeAll, afterAll, vi } from 'vitest';
+import { describe, it, expect, beforeAll, afterAll, afterEach, vi } from 'vitest';
 import { WebServer } from '../src/web/server.js';
 import { existsSync, rmSync } from 'node:fs';
 import { join } from 'node:path';
@@ -24,6 +24,17 @@ describe('Session Cleanup', () => {
     baseUrl = `http://localhost:${TEST_PORT}`;
   });
 
+  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 });
+      }
+    }
+  });
+
   afterAll(async () => {
     // Cleanup all sessions
     for (const sessionId of createdSessions) {
@@ -31,13 +42,6 @@ describe('Session Cleanup', () => {
         await fetch(`${baseUrl}/api/sessions/${sessionId}`, { method: 'DELETE' });
       } catch {}
     }
-    // Cleanup all cases
-    for (const caseName of createdCases) {
-      const casePath = join(CASES_DIR, caseName);
-      if (existsSync(casePath)) {
-        rmSync(casePath, { recursive: true, force: true });
-      }
-    }
     await server.stop();
   }, 60000);