feat(ci): add PR validation workflow

.github/workflows/ci.yml

@@ -0,0 +1,56 @@
+name: CI
+
+permissions:
+  contents: read
+
+on:
+  pull_request:
+    branches:
+      - main
+  push:
+    branches:
+      - main
+
+concurrency:
+  group: ci-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  validate:
+    name: Lint + Test + Build
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+        with:
+          submodules: recursive
+          persist-credentials: false
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v6
+        with:
+          node-version: '24'
+
+      - name: Enable Corepack
+        run: corepack enable
+
+      - name: Install Yarn
+        run: corepack prepare yarn@4.12.0 --activate
+
+      - name: Install dependencies
+        run: yarn install --immutable
+
+      - name: Generate proto clients
+        run: yarn generate
+
+      - name: Lint
+        run: yarn lint
+
+      - name: Typecheck
+        run: yarn typecheck
+
+      - name: Test
+        run: yarn test
+
+      - name: Build
+        run: yarn build