Account for GitHub Free private repos without auto-merge

[jmcte]

Summary

Dockyard inherited bootstrap governance that expects healthy PRs to converge through GitHub auto-merge. That is not currently available for OMT-Global/dockyard because the org is on GitHub Free and Dockyard is private.

Evidence

• Dockyard gh api orgs/OMT-Global reports plan free.
• Dockyard repo API reports private: true and allow_auto_merge: false after attempted enablement.
• Branch protection/ruleset APIs returned Upgrade to GitHub Pro or make this repository public to enable this feature.
• PR #62 and #63 failed Validate Merge Readiness because scripts/ci/check-pr-merge-readiness.sh required autoMergeRequest.

Desired outcome

Update bootstrap governance/templates/provisioning so private repos on plans without auto-merge use an explicit fallback merge-readiness policy instead of failing CI indefinitely.

Acceptance criteria

• Bootstrap can detect or model when auto-merge is unavailable for a target repo.
• Generated merge-readiness checks do not require autoMergeRequest when GitHub cannot support it.
• Docs/onboarding explain the fallback policy for GitHub Free private repos.
• Dockyard can consume the updated guidance without one-off policy drift.