ci: add GitHub Actions workflow for build, test, and PR benchmark

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

Author: xavierarm

.github/workflows/ci.yml

@@ -0,0 +1,87 @@
+name: CI
+
+on:
+  push:
+    branches: [main, master]
+  pull_request:
+    branches: [main, master]
+
+jobs:
+  build-and-test:
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+
+      - name: Enable pnpm
+        run: corepack enable pnpm
+
+      - name: Get pnpm store directory
+        shell: bash
+        run: |
+          echo "STORE_PATH=$(pnpm store path --silent)" >> $GITHUB_ENV
+
+      - name: Setup pnpm cache
+        uses: actions/cache@v4
+        with:
+          path: ${{ env.STORE_PATH }}
+          key: ${{ runner.os }}-pnpm-store-${{ hashFiles('**/pnpm-lock.yaml') }}
+          restore-keys: |
+            ${{ runner.os }}-pnpm-store-
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile
+
+      - name: Build
+        run: pnpm -r build
+
+      - name: Test
+        run: pnpm -r test
+
+  benchmark:
+    needs: build-and-test
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    if: github.event_name == 'pull_request'
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+
+      - name: Enable pnpm
+        run: corepack enable pnpm
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile
+
+      - name: Build
+        run: pnpm -r build
+
+      - name: Run benchmark
+        run: pnpm --filter @site-compiler/eval-benchmark test
+
+      - name: Post benchmark results
+        if: always()
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const fs = require('fs');
+            const body = '## Benchmark Results\n\nBenchmark tests completed. Check the test output above for detailed results.';
+            github.rest.issues.createComment({
+              issue_number: context.issue.number,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              body
+            });