Require status checks in the main ruleset

[MariusStorhaug]

Context and request

Protect main so a pull request cannot merge until the repository's CI checks succeed. The current ruleset requires a pull request and approval but declares no required status checks, allowing auto-merge to land on approval alone. #147 documents this gap; it does not change repository governance.

Acceptance criteria

• The main ruleset requires the CI status checks that verify this repository's pull requests.
• An auto-merge waits for those checks and the existing approval requirements.
• A pull request with a failing, pending, or absent required check cannot merge.
• The configured checks match the jobs currently expected by the repository's pull-request workflow.
• The change and its verification have durable audit evidence on this issue.

Constraints and non-goals

• Configure governance for MSXOrg/docs only; do not change workflow triggers or rulesets in other repositories.
• Do not modify the documentation delivered by 📖 [Docs]: Ready-for-review guidance now rejects missing CI checks #147.
• Release branches have no CI and no branch protection, and no checks are required anywhere PSModule/Yaml#54 tracks the separate workflow-trigger and ruleset work in PSModule/Yaml.

Technical decisions

This is an operational Task: the deliverable is a GitHub ruleset configuration, not a repository file. Apply the required-status-check rule to the existing main branch ruleset and select the CI checks emitted for pull requests. Preserve the existing deletion, non-fast-forward, linear-history, and pull-request rules.

Implementation plan

• Record the existing main ruleset and CI check names as the baseline verification evidence.
• Configure the main ruleset to require the selected CI status checks.
• Verify against a pull request that auto-merge and manual merge remain blocked while a required check is pending, failing, or absent.
• Verify that merge is permitted only after every required check succeeds and the existing approval requirements are met.
• Add an audit comment with the ruleset evidence and independent verification result.