Generate a full, in-depth guide on how to plan and execute a successful company offsite or retreat. The guide must be a complete project plan. It should include detailed sections on: 1. Goal Setting: A framework for defining the clear business objective of the retreat. 2. Agenda Design: A template for balancing work sessions, team-building activities, and downtime. 3. Logistics and Budgeting: A checklist of all logistical considerations from venue to travel. 4. A list of 10 creative and effective team-building activity ideas. 5. How to measure the ROI of the retreat. Please include a supportive disclaimer.