How the functional nodes are interconnected

What this part is for. Parts 1–5 describe what the machine does; this part describes how the code that does it is laid out, and why it is laid out that way. The short answer, in the codebase's own words, is a set of rings around a centre, each one touching only its inner neighbour through one named door — and the rest of this part makes that concrete: which ring is which directory, which door is which file, and what one real gesture looks like as it crosses every ring on its way down and back up.