RenderJson

The machine front end: the same result values Render turns into text, as JSON.

This is design/objective.md's "every step emits machine-readable output" landing: an agent drives the loop on --json and never parses prose. It exists this cheaply only because layer 1 returns values; every function here is a fold over one of them.

The encoding is deliberately hand rolled over Json rather than derived: these shapes are a public contract for tools, and a contract should not silently change because a field was renamed in a Scala case class. Each object carries a "command" discriminator so a stream of results needs no out of band context.

Every change carries its sql alongside the classification, because the reader most likely to be here is deciding whether to run it.