fix(ci): remove frontend job that references non-existent directory (#94)

The CI workflow had a `frontend` job that tried to run npm ci/build/test
in a `frontend/` directory which does not exist in this repo. The actual
UI lives in `ui/` as static HTML/CSS/JS (no Node.js toolchain). This
caused every CI run to fail on an otherwise valid codebase.

Co-authored-by: Claude Agent <claude-agent@anthropic.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -33,26 +33,6 @@ jobs:
       - name: Run tests
         run: pytest -v --tb=short tests/ || true
 
-  frontend:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v4
-
-      - name: Set up Node.js
-        uses: actions/setup-node@v4
-        with:
-          node-version: '20'
-
-      - name: Build frontend
-        working-directory: frontend
-        run: |
-          npm ci
-          npm run build
-
-      - name: Run frontend tests
-        working-directory: frontend
-        run: npx vitest run
-
   java-tests:
     runs-on: ubuntu-latest
     steps: