ci: release-please + multi-arch GHCR release workflow

- release-please: auto changelog + version bump on merge to main
- release.yml: native amd64 + arm64 builds, multi-arch manifest merge to GHCR

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

Author: syscod3

.github/workflows/release-please.yml

@@ -0,0 +1,34 @@
+name: Release Please
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+permissions:
+  contents: write
+  pull-requests: write
+  actions: write
+
+jobs:
+  release-please:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: googleapis/release-please-action@v4
+        id: release
+        with:
+          config-file: .release-please-config.json
+          manifest-file: .release-please-manifest.json
+
+      - name: Trigger release build
+        if: steps.release.outputs.release_created == 'true'
+        uses: actions/github-script@v7
+        with:
+          script: |
+            await github.rest.actions.createWorkflowDispatch({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              workflow_id: 'release.yml',
+              ref: 'main',
+              inputs: { tag: '${{ steps.release.outputs.tag_name }}' }
+            })

.github/workflows/release.yml

@@ -0,0 +1,69 @@
+name: Release
+
+on:
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: "Tag to release (e.g. v1.2.3)"
+        required: true
+
+env:
+  GO_VERSION: "1.25"
+  REGISTRY: ghcr.io
+  IMAGE: ghcr.io/syscode-labs/oci-pivot-controller
+
+jobs:
+  build-push:
+    strategy:
+      matrix:
+        include:
+          - arch: amd64
+            runner: ubuntu-24.04
+          - arch: arm64
+            runner: ubuntu-24.04-arm
+    runs-on: ${{ matrix.runner }}
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: docker/setup-buildx-action@v3
+
+      - uses: docker/login-action@v4
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - uses: docker/build-push-action@v6
+        with:
+          context: .
+          platforms: linux/${{ matrix.arch }}
+          push: true
+          tags: |
+            ${{ env.IMAGE }}:${{ inputs.tag }}-${{ matrix.arch }}
+            ${{ env.IMAGE }}:latest-${{ matrix.arch }}
+
+  merge-manifests:
+    needs: build-push
+    runs-on: ubuntu-24.04
+    permissions:
+      packages: write
+    steps:
+      - uses: docker/login-action@v4
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Create multi-arch manifests
+        run: |
+          docker buildx imagetools create \
+            -t ${{ env.IMAGE }}:${{ inputs.tag }} \
+            ${{ env.IMAGE }}:${{ inputs.tag }}-amd64 \
+            ${{ env.IMAGE }}:${{ inputs.tag }}-arm64
+          docker buildx imagetools create \
+            -t ${{ env.IMAGE }}:latest \
+            ${{ env.IMAGE }}:latest-amd64 \
+            ${{ env.IMAGE }}:latest-arm64

.release-please-config.json

@@ -0,0 +1,8 @@
+{
+  "packages": {
+    ".": {
+      "release-type": "go",
+      "include-v-in-tag": true
+    }
+  }
+}

.release-please-manifest.json

@@ -0,0 +1,3 @@
+{
+  ".": "0.0.0"
+}