Add CI workflow for tests and dist verification

This workflow ensures:
- All tests pass on PRs and main branch pushes
- Test coverage is generated
- The dist/ directory is up to date with source code

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -0,0 +1,53 @@
+name: CI
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'npm'
+      
+      - name: Install dependencies
+        run: npm ci
+      
+      - name: Run tests
+        run: npm test
+      
+      - name: Check test coverage
+        run: npm run coverage
+
+  dist-check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'npm'
+      
+      - name: Install dependencies
+        run: npm ci
+      
+      - name: Build dist
+        run: npm run build
+      
+      - name: Check if dist is up to date
+        run: |
+          if [ -n "$(git status --porcelain dist/)" ]; then
+            echo "::error::dist/ is not up to date. Please run 'npm run build' and commit the changes."
+            git diff dist/
+            exit 1
+          fi