Smalltalk and Oberon especially are complete or near complete systems: they are described from top to bottom, and in some cases described in themselves.
Oberon is interesting because the 2013 book goes much further than any recent system in this regard. One of the (final?) chapters even describes how to implement the custom processor in an FPGA.
Interlisp-D, Lisp Machines, Smalltalk, Mesa/Cedar, XDE, Oberon were an OS as IDE.
UNIX is a poor imitation of their capabilities.