docs-version-sync: source stack versions from GitHub instead of GitLab

Objective

Keep the top-of-tree documentation catalog aligned with the latest stable self-managed stack release from the public NVIDIA/nvcf repository. Public artifact availability remains a separate, explicit decision because NGC publication occurs after QA qualification.

Current flow

1. The stack release workflow resolves the control-plane, compute-plane, and observability Helmfile states from the exact tagged commit.
2. The workflow attaches nvcf-self-managed-stack-inventory.json to the GitHub stack release.
3. tools/docs-version-sync selects the latest stable deploy/stacks/self-managed/vX.Y.Z GitHub release, downloads that inventory, and validates its tag, commit, and effective stack pins.
4. The catalog maps resolved artifacts to public catalog destinations. Exact available versions are recorded in publications; unavailable versions are recorded in publication_pending and never render private locations.
5. The tool updates docs/version-catalog/main.yaml and the generated blocks in the top-of-tree user docs.

The release inventory must exist before the docs catalog can advance. Public NGC publication can happen later. When QA publishes an artifact, update its exact public availability record separately.

Commands

Update the catalog and generated documentation:

go run -C tools/docs-version-sync . --target main --update-catalog

Run the offline consistency check:

./tools/ci/check-doc-version-sync

Compare the checked-in catalog with the latest stable GitHub stack release:

./tools/ci/check-doc-version-current-release

Work tracking

Implementation tasks are attached directly as sub-issues. The final terminology and dead-code cleanup is tracked by #1812.

Completion criteria

• A fresh public GitHub checkout can update the catalog without private source-control inputs.
• The generated catalog covers all three deployment bundles and their resolved artifacts from one immutable stack release.
• Generated docs contain only public catalog locations or Publication pending.
• Offline and current-release checks enforce catalog freshness in GitHub CI.

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