Harden Merge and Automation Policy

[FMCalisto]

This issue tracks the remaining work needed to make the source template repository enforcement model consistent on GitHub.

Scope:

• verify the baseline workflow set that should remain required on the source template
• add required status checks to branch protection once the relevant workflows are present on main
• review whether merge strategy defaults and branch rules match the intended maintainer workflow

Acceptance criteria:

• the source template has a documented and enforceable merge path
• required checks on main match workflows that actually run on the default branch
• repository documentation reflects the final merge and automation policy

Validation expectations:

• confirm the protection rules through the GitHub API or repository settings
• verify that the required checks exist and report on pull requests as expected