ci: build each arch on native runners instead of QEMU

.github/workflows/docker-publish.yml

@@ -15,19 +15,42 @@ env:
   IMAGE_NAME: ${{ github.repository }}
 
 jobs:
-  build-and-push:
-    runs-on: ubuntu-latest
+  # Build each architecture on its own native runner. No QEMU emulation, so
+  # better-sqlite3 compiles natively instead of taking ~30min under qemu (and
+  # risking a broken arm64 binary from an emulated node-gyp crash).
+  build:
+    name: Build ${{ matrix.platform }}
+    runs-on: ${{ matrix.runner }}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - platform: linux/amd64
+            runner: ubuntu-latest
+          - platform: linux/arm64
+            runner: ubuntu-24.04-arm
     permissions:
       contents: read
       packages: write
 
     steps:
+      - name: Prepare platform name
+        run: echo "PLATFORM_PAIR=${platform//\//-}" >> $GITHUB_ENV
+        env:
+          platform: ${{ matrix.platform }}
+
       - name: Checkout repository
         uses: actions/checkout@v4
 
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
 
+      - name: Extract metadata (labels) for Docker
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+
       - name: Log in to GitHub Container Registry
         if: github.event_name != 'pull_request'
         uses: docker/login-action@v3
@@ -36,7 +59,57 @@ jobs:
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
-      - name: Extract metadata (tags, labels) for Docker
+      # On pull requests this only validates the build: push=false, no digest is
+      # exported, and the merge job below is skipped.
+      - name: Build and push by digest
+        id: build
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          platforms: ${{ matrix.platform }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha,scope=${{ env.PLATFORM_PAIR }}
+          cache-to: type=gha,mode=max,scope=${{ env.PLATFORM_PAIR }}
+          outputs: type=image,name=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }},push-by-digest=true,name-canonical=true,push=${{ github.event_name != 'pull_request' }}
+
+      - name: Export digest
+        if: github.event_name != 'pull_request'
+        run: |
+          mkdir -p /tmp/digests
+          digest="${{ steps.build.outputs.digest }}"
+          touch "/tmp/digests/${digest#sha256:}"
+
+      - name: Upload digest
+        if: github.event_name != 'pull_request'
+        uses: actions/upload-artifact@v4
+        with:
+          name: digests-${{ env.PLATFORM_PAIR }}
+          path: /tmp/digests/*
+          if-no-files-found: error
+          retention-days: 1
+
+  # Stitch the per-arch images into a single multi-arch manifest under the real tags.
+  merge:
+    name: Merge manifests
+    if: github.event_name != 'pull_request'
+    runs-on: ubuntu-latest
+    needs: [build]
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - name: Download digests
+        uses: actions/download-artifact@v4
+        with:
+          path: /tmp/digests
+          pattern: digests-*
+          merge-multiple: true
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Extract metadata (tags) for Docker
         id: meta
         uses: docker/metadata-action@v5
         with:
@@ -49,13 +122,20 @@ jobs:
             type=semver,pattern={{major}}
             type=raw,value=latest,enable={{is_default_branch}}
 
-      - name: Build and push Docker image
-        uses: docker/build-push-action@v5
+      - name: Log in to GitHub Container Registry
+        uses: docker/login-action@v3
         with:
-          context: .
-          push: ${{ github.event_name != 'pull_request' }}
-          tags: ${{ steps.meta.outputs.tags }}
-          labels: ${{ steps.meta.outputs.labels }}
-          cache-from: type=gha
-          cache-to: type=gha,mode=max
-          platforms: linux/amd64,linux/arm64
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Create manifest list and push
+        working-directory: /tmp/digests
+        run: |
+          docker buildx imagetools create \
+            $(jq -cr '.tags | map("-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
+            $(printf '${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}@sha256:%s ' *)
+
+      - name: Inspect image
+        run: |
+          docker buildx imagetools inspect ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ steps.meta.outputs.version }}