chore: add concurrency and run name configuration to rollout workflow

[mnkiefer]

• Updates the workflow configuration in the central-repo-ops documentation to improve concurrency handling, workflow naming.

[Copilot]

Pull request overview

This PR enhances the CentralRepoOps documentation by adding concurrency controls and run name configuration to the Dependabot rollout worker workflow example. These additions help prevent workflow conflicts when multiple rollouts target the same repository and provide better workflow run visibility.

Changes:

• Added run-name configuration to display the target repository in workflow runs
• Added workflow-level concurrency control to prevent multiple runs for the same target repository
• Added engine-level concurrency control to isolate AI execution per repository
• Added persist-credentials: false to the checkout action as a security best practice

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[Copilot]

The addition of persist-credentials: false is not mentioned in the PR title or description, which only references adding concurrency and run name configuration. While setting persist-credentials: false is a security best practice when using a custom token (to prevent the token from being persisted in the Git config), this change should be documented in the PR description to ensure it's an intentional modification rather than an accidental inclusion.