[#47] Add support for Dockerfiles + publishing.

- Added template Dockerfile and entrypoint.sh
- Added test-docker.yml workflow (build + hadolint lint)
- Added release-docker.yml workflow (multi-arch push to Docker Hub)
- Added 'Use Docker' prompt to init.sh (defaults to No)
- Added Docker image name prompt (defaults to namespace/project)
- Added remove_docker() function for cleanup when Docker not selected
- Added DOCKER token blocks to CLAUDE.md
- Added 'docker' test case to InitTest.php
- Updated test fixtures via snapshot auto-update
- All 14 init tests passing

Author: StevenWalker98

.github/workflows/release-docker.yml

@@ -0,0 +1,44 @@
+name: Release Docker
+
+on:
+  push:
+    tags:
+      - '*'
+
+permissions:
+  contents: read
+
+jobs:
+  push-release-to-registry:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v6
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to Docker Hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKER_USER }}
+          password: ${{ secrets.DOCKER_PASS }}
+
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: yournamespace/yourproject
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          platforms: linux/x86_64,linux/arm64

.github/workflows/test-docker.yml

@@ -0,0 +1,56 @@
+name: Test Docker
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+      - 'feature/**'
+  workflow_dispatch:
+    inputs:
+      enable_terminal:
+        type: boolean
+        description: 'Enable terminal session.'
+        required: false
+        default: false
+
+permissions:
+  contents: read
+
+jobs:
+  test-docker:
+    name: Docker
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v6
+
+      - name: Lint Dockerfile
+        uses: hadolint/hadolint-action@v3.1.0
+        with:
+          dockerfile: Dockerfile
+        continue-on-error: ${{ vars.CI_LINT_IGNORE_FAILURE == '1' }}
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Build Docker image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          push: false
+          load: true
+          tags: yournamespace/yourproject:test
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+
+      - name: Test Docker image
+        run: docker run --rm yournamespace/yourproject:test
+
+      - name: Setup tmate session
+        if: ${{ !cancelled() && github.event.inputs.enable_terminal }}
+        uses: mxschmitt/action-tmate@v3
+        timeout-minutes: 30

.scaffold/docs/content/docker/README.mdx

@@ -0,0 +1,81 @@
+---
+title: Docker
+sidebar_position: 6
+---
+
+# Docker
+
+This scaffold provides optional Docker support for building and publishing
+container images. When enabled during initialization, it includes a Dockerfile,
+an entrypoint script, and GitHub Actions workflows for testing and releasing
+Docker images.
+
+## Dockerfile
+
+The included `Dockerfile` uses a minimal Alpine Linux base image with Bash
+installed. It follows OCI image labeling conventions and uses a dedicated
+entrypoint script.
+
+```dockerfile
+FROM alpine:3
+
+RUN apk add --no-cache bash
+
+COPY entrypoint.sh /usr/local/bin/entrypoint.sh
+
+ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]
+```
+
+## Entrypoint
+
+The `entrypoint.sh` script enforces strict shell options (`set -euo pipefail`)
+and forwards arguments to the container command.
+
+## Building and running
+
+```bash
+# Build the image
+docker build -t yournamespace/yourproject .
+
+# Run the container
+docker run --rm yournamespace/yourproject
+```
+
+## Linting
+
+The Dockerfile is linted using [Hadolint](https://github.com/hadolint/hadolint),
+a Dockerfile linter that helps enforce best practices.
+
+```bash
+# Lint locally
+hadolint Dockerfile
+```
+
+Linting also runs automatically in CI via the `test-docker.yml` workflow.
+
+## CI/CD workflows
+
+### Testing (`test-docker.yml`)
+
+Runs on pushes to `main` and pull requests. This workflow:
+
+1. Lints the Dockerfile with Hadolint
+2. Builds the Docker image using Docker Buildx
+3. Runs the container to verify it starts correctly
+
+### Release (`release-docker.yml`)
+
+Runs on tag pushes. This workflow:
+
+1. Sets up QEMU and Docker Buildx for multi-architecture builds
+2. Authenticates with Docker Hub
+3. Builds and pushes multi-arch images (`linux/x86_64`, `linux/arm64`)
+
+#### Docker Hub credentials
+
+The release workflow requires the following repository secrets:
+
+- `DOCKER_USER` — Docker Hub username
+- `DOCKER_PASS` — Docker Hub access token
+
+Set these in your repository's **Settings > Secrets and variables > Actions**.

.scaffold/docs/cspell.json

@@ -11,6 +11,7 @@
         "GHSA",
         "Terminalizer",
         "autoloader",
+        "Buildx",
         "calver",
         "cobertura",
         "daemonized",

.scaffold/tests/phpunit/fixtures/init/_baseline/docs/cspell.json

@@ -10,6 +10,7 @@
         "Cobertura",
         "Terminalizer",
         "autoloader",
+        "Buildx",
         "calver",
         "cobertura",
         "daemonized",