Generate a full detail guide on managing co-founder conflict. The guide must be a compassionate and structured resource. It should include detailed sections on: 1. The most common sources of co-founder conflict (e.g., vision, roles, equity). 2. A framework for a structured 'State of the Union' conversation to have regularly. 3. A step-by-step mediation process for resolving specific disagreements. 4. The importance of a Founders' Agreement as a foundational document. 5. When and how to bring in an external mediator or advisor. Please include a strong disclaimer about seeking professional mediation or legal advice.