The progress tracker API lets you model a tree of steps, along the same structure as protocols and subprotocols. Each step has an (optionally changing) label, and thus progress trackers can be arranged in a tree. Updates to the progress at each level flow up the tree via an RxJava observable (I guess we will use this more in future).
A simple console renderer is provided that uses ANSI escapes and Emoji to show animated progress through a protocol.
The trader demo is enhanced to use this framework, when run outside of Gradle.