feat: add GitHub Actions CI workflow for typecheck and lint

.github/workflows/ci.yml

@@ -0,0 +1,91 @@
+name: CI
+
+on:
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  typecheck-client:
+    name: Typecheck Client
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: "npm"
+          cache-dependency-path: client/package-lock.json
+
+      - name: Install dependencies
+        run: npm ci
+        working-directory: client
+
+      - name: Run TypeScript check
+        run: npx tsc --noEmit
+        working-directory: client
+
+  typecheck-server:
+    name: Typecheck Server
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: "npm"
+          cache-dependency-path: server/package-lock.json
+
+      - name: Install dependencies
+        run: npm ci
+        working-directory: server
+
+      - name: Run TypeScript check
+        run: npx tsc --noEmit
+        working-directory: server
+
+  lint-client:
+    name: Lint Client
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: "npm"
+          cache-dependency-path: client/package-lock.json
+
+      - name: Install dependencies
+        run: npm ci
+        working-directory: client
+
+      - name: Run ESLint
+        run: npx eslint . --ext .ts,.tsx
+        working-directory: client
+
+  lint-server:
+    name: Lint Server
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: "npm"
+          cache-dependency-path: server/package-lock.json
+
+      - name: Install dependencies
+        run: npm ci
+        working-directory: server
+
+      - name: Run ESLint
+        run: npx eslint . --ext .ts
+        working-directory: server