Fabric

Deep dive on the underlying half of the interaction model: Fabrics and the Context that binds them.

1. 00-fabric.md - what a Fabric is: address space and resolution capability.
2. 01-context.md - Context as the union of Fabrics a program runs against.
3. 02-protocol.md - how a Ref finds its Fabric: type, tags, predicates, fallback.