Add docs for double agent scenario
This document contains tips, workflows, and more for developing within this repository.
-## Local Development
+## Design for Fleet Managing Fleet: Hosted Rancher, Harvester, Rancher Managing Rancher, etc.
+
+Starting with Fleet v0.3.7 and Rancher v2.6.1, scenarios where Fleet is managing Fleet (standalone or Rancher managing Rancher) will result in _two_ `fleet-agent` deployments running every _managed_ Fleet cluster.
+The agents will be communicating with two different `fleet-controller` deployments.
+
+```
+Local Fleet Cluster Managed Fleet Cluster Downstream Cluster
+=================== ======================== ======================
+fleet-controller <-------> fleet-agent (downstream)
+fleet-agent (local) fleet-controller <------------> fleet-agent (downstream)
+ fleet-agent (local)
+```
+
+## Local Development Workflow: Standlone Fleet and Fleet in Rancher
All steps in this guide assume your current working directory is the root of the repository.
Moreover, this guide was written for Unix-like developer environments, so you may need to modify some steps if you are using a non-Unix-like developer environment (i.e. Windows).
