Add Copilot-Instructions label policy rule

[Demitrius Nelon (denelon)]

📖 Description

Adds a new policy-bot configuration (.github/policies/labelManagement.issueOpened.yml, which did not previously exist in this repo) with a rule that automatically applies a Copilot-Instructions label to pull requests that modify .github/copilot-instructions.md or any .github/instructions/*.instructions.md file, so reviewers get extra visibility when Copilot's guidance changes.

The rule triggers on PR Opened and Synchronize, matches files via regex, and is guarded with a
ot: hasLabel check so it won't re-fire once the label is already applied. It intentionally contains only this one rule and does not copy any unrelated rules from sibling repos.

Created with GitHub Copilot's assistance.

🔗 References

Closes #319

🔍 Validation

• Validated the YAML with PowerShell's powershell-yaml module (ConvertFrom-Yaml).
• Cross-checked all conditions/actions against the documented GitOps.PullRequestIssueManagement policy schema.

✅ Checklist

• Signed the Contributor License Agreement
• Linked to an issue
• Updated documentation (if applicable)
• Updated Copilot instructions (if build, architecture, or conventions changed)

📋 Issue Type

• Bug fix
• Feature
• Task