[WIP] Collect successful PR-check.yaml executions in CSV

[Copilot]

• Inspect repository and identify the PR checks workflow file and workflow id
• Collect successful PR checks workflow runs from 2026-01-01 to today using GitHub GraphQL with minimal fields
• Generate CSV with columns run_id, started_at, completed_at
• Add the CSV file to the repository in a minimal, appropriate location
• Verify formatting/content and run required review/security checks

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[cla-bot]

We require contributors to sign our Contributor License Agreement. For us to review and merge your code, don't hesitate to get in touch with @chrisjroyce, @TristramN or @mharvey83 to get yourself added.