Start here.
Three documents. The quick start gets it running; the other two are for when you want to know why something is the way it is.
Quick start
From nothing to a machine showing green. The server, then the agent, then a first project.
ReferenceInstallation
The full server setup: environment, database, reverse proxy, process manager, and the agent on each machine.
ReferenceAPI
The HTTP contract for native clients — authentication, bearer tokens, and where the OpenAPI document lives.
The rest is in the repository.
The architecture map, the narrative product guide, and the design documents behind each feature live alongside the code, because that is the only place they stay true. If you are about to change something, read the document that covers it first — several of them exist specifically to record why an obvious approach was the wrong one.