Add agentless report-green pipeline for docs-only PRs

[Copilot]

Fixes #54148

Documentation-only PRs (e.g. #54136) skip every other CI pipeline, leaving Build Analysis hung waiting for a status that never arrives — today the only workaround is a manual ba-g comment.

Changes

• eng/pipelines/report-green.yml — new PR-only pipeline mirroring the current dotnet/runtime pattern. Path filter matches the docs/infra files that no-op the rest of CI (**/*.md, documentation/*, .github/*, .devcontainer/*, .vscode/*, top-level license/notice/readme files).
• Single Report_Green job on pool: server (agentless) using Delay@1 with delayForMinutes: '0' — no agent leased, no VM spun up, completes immediately, gives BA its green check.

jobs:
  - job: Report_Green
    pool: server
    steps:
    - task: Delay@1
      inputs:
        delayForMinutes: '0'

Note

Requires a corresponding pipeline definition wired up in dnceng AzDO before it takes effect.

[Copilot]

Pull request overview

Adds a new PR-only Azure Pipelines definition intended to report a successful Build Analysis status for documentation/infra-only changes that skip the main CI pipeline.

Changes:

• Adds eng/pipelines/report-green.yml.
• Configures PR path filters for docs/infra files.
• Adds an agentless Report_Green server job using Delay@1 as a no-op success task.

[lbussell]

Thanks for the review @akoeplinger - It's copied pretty much wholesale from runtime so I expect it to work.