Add CODEOWNERS for GitHub Copilot directories

[mccoyp]

Description

This adds Libba and me as code owners for GitHub Copilot directories for agents, prompts, and skills so we can check in to maintain best practices as teams incorporate these tools into their workflows.

All SDK Contribution checklist:

• The pull request does not introduce [breaking changes]
• CHANGELOG is updated for new features, bug fixes or other significant changes.
• I have read the contribution guidelines.

General Guidelines and Best Practices

• Title of the pull request is clear and informative.
• There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For more information on cleaning up the commits in your PR, see this page.

Testing Guidelines

• Pull request includes test coverage for the included changes.

[Copilot]

Pull request overview

This PR adds CODEOWNERS entries for GitHub Copilot-related directories to establish ownership and maintain best practices as teams adopt these tools in their workflows. The additions assign @mccoyp and @l0lawrence as code owners for GitHub Copilot infrastructure.

Changes:

• Added CODEOWNERS entries for .github/agents, .github/prompts, and .github/skills directories