Docs: Add offline deployment guide for GitLab Duo Self-Hosted

Andrew Dunnrequested to merge
docs/duo-self-hosted-offline-deployment into master

What does this MR do?

Add an offline deployment guide for GitLab Duo Self-Hosted at doc/administration/gitlab_duo_self_hosted/offline_deployment.md and add a link from the offline topics hub page.

This page documents:

  • Complete artifact manifest (3 container images + LLM model weights) with source registries, tag formats, and sizes
  • Transfer procedure using skopeo copy (with docker save fallback), following the precedent set by the security scanner offline docs
  • AI Gateway startup with offline-specific configuration (DUO_WORKFLOW_AUTH__OIDC_CUSTOMER_PORTAL_URL= empty string)
  • vLLM startup with transferred model weights
  • GitLab administration configuration for internal registries
  • Custom executor image with duo-cli pre-installed for offline Agent Platform Flows (requires GitLab 18.9 or later)
  • Deployment verification steps
  • Self-signed certificate guidance for internal registries

Also adds an entry to doc/topics/offline/_index.md under ## Features so the offline topics hub links to this page.

Dependencies

This MR must merge after !231001 (offline flow execution guide), which adds the #use-a-custom-image-in-an-offline-environment anchor linked from the new page. The docs-lint links job will fail until !231001 merges.

Related issues

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/596901

Related:

Author's checklist

Reviewer's checklist

Documentation-related MRs should be reviewed by a Technical Writer for a non-blocking review, based on Documentation Guidelines and the Style Guide.

  • If the content requires it, ensure the information is reviewed by a subject matter expert.
  • Technical writer review items:
    • Ensure docs metadata is present and up-to-date.
    • Ensure the appropriate labels are added to this MR.
    • Ensure a release milestone is set.
    • If relevant to this MR, ensure content topic type principles are in use, including:
      • The headings should be something you'd do a Google search for.
      • The headings (other than the page title) should be active.
      • Any task steps should be written as a numbered list.
  • Review by assigned maintainer, who can always request/require the reviews above.

AI-Generated Content Disclosure: This MR contains documentation drafted with assistance from Claude Code. The artifact inventory was verified against the GitLab Container Registry, Docker Hub, and npm. The transfer procedures follow established patterns from the security scanner offline docs. The full transfer chain, AI Gateway startup, vLLM model serving, and duo-cli executor build were lab-validated on GCE (CentOS Stream 10, 2x A100 40GB, podman 5.8.0) with all steps passing.

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