fix(ui): add vitest dep + --passWithNoTests so test script doesn't fail

The test script referenced vitest without declaring the devDep, and vitest
exits non-zero when no test files match. Adds the missing dep and the flag
to keep CI green for empty test suites.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

pnpm-lock.yaml

@@ -338,6 +338,9 @@ importers:
       tailwindcss:
         specifier: ^4.1.0
         version: 4.2.2
+      vitest:
+        specifier: ^3.1.0
+        version: 3.2.4(@types/debug@4.1.13)(@types/node@25.5.2)(happy-dom@20.8.9)(jiti@2.6.1)(lightningcss@1.32.0)(sass@1.99.0)(tsx@4.21.0)
 
 packages: