Document branch protection rules and settings

[RAprogramm]

Objective

Document recommended branch protection rules for the masterror repository to maintain code quality and enforce review processes.

Background

Phase 2.2 from KaiCode 2026 preparation (#205). Branch protection rules cannot be automated via PR but should be documented for maintainers to configure manually.

Tasks

Documentation

• Create docs/BRANCH_PROTECTION.md with recommended settings
• Document protection rules for main branch
• Document protection rules for release branches
• Add rationale for each rule

Recommended Rules for Main Branch

Required Status Checks:

• Require branches to be up to date before merging
• Require ci / fmt to pass
• Require ci / clippy (MSRV) to pass
• Require ci / clippy (stable) to pass
• Require ci / test (MSRV) to pass
• Require ci / test (stable) to pass
• Require ci / coverage to pass
• Require ci / deny to pass
• Require ci / audit to pass

Pull Request Requirements:

• Require at least 1 approval
• Dismiss stale reviews on new commits
• Require review from code owners (if CODEOWNERS file exists)

Additional Restrictions:

• Require linear history (no merge commits)
• Do not allow bypassing settings (even for admins)
• Require signed commits (optional, document pros/cons)

Manual Setup Steps

Document step-by-step:

1. Navigate to Settings → Branches
2. Add branch protection rule for main
3. Configure each setting with screenshots
4. Verify rules are active

Success Criteria

• Documentation file created with all settings
• Rationale provided for each rule
• Manual setup instructions with screenshots
• Link added to CONTRIBUTING.md

Priority

Medium (manual setup, not blocking)

Related

• Prepare repository for KaiCode 2026 competition #205 KaiCode 2026 preparation