Add CI typecheck workflow

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: shixish

.github/workflows/ci.yml

@@ -0,0 +1,18 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  typecheck:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: npm
+      - run: npm ci
+      - run: npm run typecheck

.gitignore

@@ -2,3 +2,5 @@ node_modules/
 dist/
 *.tsbuildinfo
 .DS_Store
+PLAN.md
+*.tgz