[gh bot] Add another agent to do validations before we publish the reply

We want to ensure certain guidelines are followed in our responses.

For example, we should never suggest that customers avoid using the Azure SDK.

To achieve this consistently, we need a dedicated agent.

No files, tests, or entry points are identified. Start by locating the gh bot's reply-publication flow and defining how a dedicated validation agent should enforce response guidelines, including the Azure SDK rule. Done means responses are validated against the agreed guidelines before publication.

Written by the indexing model from the issue text.