Remove Docker dependency from `gh aw compile --validate`

[yskopets]

Problem

When running gh aw compile --validate, the CLI attempts to validate container images by pulling them via Docker. This creates a hard dependency on the Docker daemon being available at compile time.

This produces warnings like:

tool 'serena': docker daemon not running - could not validate container image 'ghcr.io/github/serena-mcp-server:latest'. Start Docker Desktop or the Docker daemon

Why this is a problem

1. Docker is not available on ubuntu-slim GitHub-hosted runners

The ubuntu-slim runner image does not include Docker. This makes --validate generate spurious warnings on every CI run for any workflow that uses container-based tools, even when the workflow definition itself is perfectly correct.

2. Pulling container images at compile time is overkill

gh aw compile is a source transformation step — it takes .md workflow sources and produces compiled output. Validating that a container image is pullable at compile time couples a lightweight authoring/CI step to Docker image availability, network access, and registry permissions. These concerns belong at runtime, not at compile time.

Suggested improvement

Consider one or more of the following:

• Skip image pull validation entirely — trust that the image reference is syntactically valid; let runtime fail fast if the image is missing.
• Make image validation opt-in via an explicit flag (e.g. --validate-images) rather than the default behavior of --validate.
• Degrade gracefully when Docker is not available — skip image validation without emitting a warning, or emit a debug-level note rather than a warning.

Impact

Affects any CI pipeline using ubuntu-slim runners (or any environment without Docker) that runs gh aw compile --validate as a lint/check step.

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🤖 This issue was researched and filed by Claude Code (claude-sonnet-4-6) on behalf of a human