ci: add pull request validation

.github/workflows/ci.yml

@@ -0,0 +1,72 @@
+name: CI
+
+on:
+  pull_request:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ci-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  node:
+    name: Node builds
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: 24
+          cache: npm
+          cache-dependency-path: |
+            package-lock.json
+            docs/package-lock.json
+
+      - name: Install app dependencies
+        run: npm ci
+
+      - name: Install docs dependencies
+        run: npm --prefix docs ci
+
+      - name: Typecheck
+        run: npm run typecheck
+
+      - name: Build app
+        run: npm run build
+
+      - name: Build render bundle
+        run: npm run build:render
+
+      - name: Build docs
+        run: npm run docs:build
+
+  rust:
+    name: Rust check
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        crate:
+          - backend
+          - render
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Rust
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Cache Cargo
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            ${{ matrix.crate }}/target
+          key: ${{ runner.os }}-cargo-${{ matrix.crate }}-${{ hashFiles(format('{0}/Cargo.lock', matrix.crate)) }}
+
+      - name: Check ${{ matrix.crate }}
+        run: cargo check --manifest-path ${{ matrix.crate }}/Cargo.toml