ci: add CI workflow for format, typecheck, and test

Runs on push/PR to main. Also adds skipLibCheck to tsconfig to silence
pre-existing errors in vite/vitest declaration files that don't affect
the Worker build.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -0,0 +1,30 @@
+name: CI
+
+on:
+  push:
+    branches: ["main"]
+  pull_request:
+    branches: ["main"]
+
+jobs:
+  ci:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+
+      - uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4
+        with:
+          node-version: 22
+          cache: npm
+
+      - run: npm ci
+
+      - name: Format check
+        run: npx prettier --check '**/*.{js,ts,css,json,md}'
+
+      - name: Type check
+        run: npm run typecheck
+
+      - name: Test
+        run: npm test

tsconfig.json

@@ -11,7 +11,8 @@
     "noEmit": true,
     "isolatedModules": true,
     "allowJs": true,
-    "forceConsistentCasingInFileNames": true
+    "forceConsistentCasingInFileNames": true,
+    "skipLibCheck": true
   },
   "include": ["src/**/*"],
   "exclude": ["node_modules", "dist"]