Rationale
A key nobody reads is a typo that silently does nothing, which is worse than a refusal; the allowlists under share/allow/ are the schema, and a field written and never read is a second source of truth.
Required behaviour
Every configuration file rejects a key nothing reads, and every state field is both written and read.
Failure behaviour
No command decides this rule; a reviewer does, and a change that violates it is not merged. Where a behavioural case covers part of it, that case is named below.
Verification
Review. test/cases/00_yaml_flatten.sh and the policy, profile, manifest and rule allowlists under share/allow/.