fix: Repair test harness coverage, excludes, and timer overhead

- Add @vitest/coverage-v8 dep so `npm run test:coverage` actually works
- Add exclude patterns to vitest config (node_modules, dist, packages)
- Replace dynamic import('vitest') in advanceTimers with direct vi import

src/test/harness.ts

@@ -7,6 +7,7 @@
  */
 
 import { randomUUID } from 'crypto';
+import { vi } from 'vitest';
 import type { DrizzleDatabase } from '../db/index.js';
 import type { EventBus, DomainEvent } from '../events/types.js';
 import { EventEmitterBus } from '../events/bus.js';
@@ -510,11 +511,7 @@ export function createTestHarness(): TestHarness {
     },
 
     // Timer helper - requires vi.useFakeTimers() to be active
-    advanceTimers: async () => {
-      // Dynamic import to avoid vitest dependency at runtime
-      const { vi } = await import('vitest');
-      await vi.runAllTimersAsync();
-    },
+    advanceTimers: () => vi.runAllTimersAsync(),
 
     // ========================================================================
     // Architect Mode Helpers