fix(dashboard): exclude Playwright specs from Vitest

npm test (vitest run) collected tests/a11y.spec.ts, a Playwright spec,
and failed. Exclude tests/** from Vitest and pass when no unit tests
exist; Playwright specs still run via npm run test:e2e / test:a11y.

Co-Authored-By: claude-flow <ruv@ruv.net>

dashboard/vite.config.ts

@@ -1,3 +1,4 @@
+/// <reference types="vitest/config" />
 import { defineConfig } from 'vite';
 import { VitePWA } from 'vite-plugin-pwa';
 
@@ -66,6 +67,11 @@ export default defineConfig({
       },
     },
   },
+  test: {
+    // tests/ holds Playwright specs (run via `npm run test:e2e`), not Vitest.
+    exclude: ['**/node_modules/**', '**/dist/**', 'tests/**'],
+    passWithNoTests: true,
+  },
   server: {
     port: 5173,
     strictPort: true,