Configuration Schema Migration

Read the complete procedure (skill file) before changing a
configuration schema, serialized representation, environment mapping, loader,
validator, or generated configuration contract.

One approved migration produces one final contract. It rewires every scoped
producer and consumer, rejects the old format, deletes superseded paths, proves
idempotence, and validates the real runtime before tests. Canonical calculated
defaults are declared once and omitted from environment variables, settings,
parameters, arguments, and persisted config. Only non-derivable current values
are required. No dual read/write, compatibility shim, fallback, competing or
default-on-error value, or deferred cleanup is permitted.