Edit: Finished reading, what a great project! I've looked for something like this before, but ssh documentation never quite contained what I was looking for, let alone providing a simple client to hack with.
Many code snippets look a lot easier than I would expect it to be (e.g. DH KEX looks very simple there), though of course finding out what the correct code is, even if it's brief, takes a lot of effort.
Great writeup and thanks for sharing!