API for registry.

A registry is a vector-based collection of command specifications that define how to
recognize, validate, and execute commands found in instruction map.
Vector order defines the command scan priority.

Input (user-facing):
  (registry/build
    [cmds/command-from-spec cmds/command-fn-spec])

Output (built registry):
  {:registry           [command-from-spec command-fn-spec]
   :registry-validated 1709654400000
   :registry-hash      12345}