Pull Subscriber Onboarding and Documentation (Phase 1 C)

Phase: 1C (documentation, runs in parallel with or after Phase 1 B+C+D)
Labels: quartz, phase-1, documentation

Context

Once status.json is being published (Phase 1 B+C), downstream projects can poll it
without any GitHub App installation. This issue covers the template and documentation
that enables them to do so, and updates the README from its initial stub to a proper
onboarding guide.

Reference: RFC-0011 (ROCm/TheRock#3728 / docs/rfcs/RFC0011-Quartz-CICD-Datahub.md in ROCm/TheRock once merged) — Phase 1, Section C.

Tasks

Pull subscriber template

• templates/subscriber-pull.yml: example scheduled workflow for downstream projects
  to poll status.json via raw GitHub URL — no GitHub App installation required
• Document the available polling endpoints:
  • release-nightly/<date>/status.json
  • release-nightly/latest.json — most recent nightly
  • release-nightly/latest_good.json — most recent fully-passing nightly
  • prerelease/<version>/status.json
  • prerelease/latest.json — most recent prerelease

Documentation and README

• docs/pull-subscription.md: full guide for pull subscribers — how to poll
  status.json, available endpoints, example using templates/subscriber-pull.yml
• Update README.md to explain what Quartz is and what data it publishes, and
  link to RFC-0011 and the relevant docs/ pages

Notes

• latest_good.json: definition of "fully passing" is still TBD — e.g. all
  architectures pass, or a required subset; whether PyTorch and JAX are required or
  ROCm-only. This must be decided before generate_status_json.py can populate it
  (Phase 1 B+C issue).
• templates/subscriber-push.yml and the PR template for push subscription are covered
  in Phase 2 A (after Quartz Conveyor is implemented).
• templates/downstream-send.yml (reporting results back) is covered in Phase 3.

Start by reviewing templates/subscriber-pull.yml, docs/pull-subscription.md, README.md, and the referenced RFC-0011 section. Verify that the guide explains each listed status.json endpoint, demonstrates the subscriber template, and links the relevant documentation; the issue is complete when those documentation and template tasks are confirmed.