Harden Docker workflow against transient Buildx bootstrap timeouts

[Copilot]

Build (linux/amd64) was failing before any image build work due to intermittent timeouts while docker/setup-buildx-action bootstrapped BuildKit from Docker Hub. This change makes Buildx setup resilient to one transient failure without changing normal-path behavior.

• Root cause addressed

  • Setup Docker buildx could fail on a single network/auth timeout to Docker Hub (moby/buildkit:buildx-stable-1 pull path), causing the whole job to abort early.

• Workflow reliability changes

  • In .github/workflows/docker.yaml, both build and merge jobs now:
    • run an initial Buildx setup step with continue-on-error: true
    • run a second setup attempt only if the first attempt failed
  • Retains existing skip gating (env.SKIP != 'true') so retry logic only applies when the job is intended to run.

• Behavioral impact

  • No change on successful first attempt.
  • Single transient Buildx bootstrap failure no longer fails the job immediately.

- name: Setup Docker buildx
  if: env.SKIP != 'true'
  id: setup-buildx
  uses: docker/setup-buildx-action@v3
  continue-on-error: true

- name: Retry setup Docker buildx
  if: env.SKIP != 'true' && steps.setup-buildx.outcome == 'failure'
  uses: docker/setup-buildx-action@v3

[Copilot]

Pull request overview

This PR hardens the Docker GitHub Actions workflow against intermittent docker/setup-buildx-action bootstrap failures (e.g., transient Docker Hub pull/auth timeouts) by adding a single retry path while preserving the normal success behavior.

Changes:

• Adds an initial docker/setup-buildx-action@v3 step with continue-on-error: true and a step id to capture its outcome.
• Adds a second “retry” Buildx setup step that runs only when the first attempt fails (and only when env.SKIP != 'true').

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