Create a v3 kit

A kit is one OCI image. Its layers are the content and its manifest annotation carries the descriptor: what the kit offers, what it needs from the host as typed capability requests, and what it needs from other kits. An engine that does not read the annotation runs it as an ordinary image.

To migrate an existing v2 spec.yaml kit rather than write a new one, use the migrate-kit-to-v3 skill instead; its FIELD-MAPPING.md is also the best field-by-field reference if you are unsure what a given declaration means.

Decide the kind first

Everything else follows from this.