chore(test): ignore coverage and vitest artifacts

Add `coverage/`, `__screenshots__/`, and `.vitest-attachments/`
to `.gitignore`, and configure Vitest coverage exclusions in `vite.config.ts.`

.gitignore

@@ -24,3 +24,10 @@ dist-ssr
 *.njsproj
 *.sln
 *.sw?
+
+# Test coverage
+/coverage
+
+# Vitest artifacts (browser screenshots/attachments)
+**/__screenshots__/
+.vitest-attachments/

vite.config.ts

@@ -28,5 +28,8 @@ export default defineConfig({
       provider: playwright(),
       instances: [{ browser: 'chromium' }],
     },
+    coverage: {
+      exclude: ['src/components/ui/**', 'src/assets/**'],
+    },
   },
 })