"Protocol Owned by Client" Rule

• The client defines and owns the dependency shape (protocol/interface/data model).
• A protocol MUST live in the same module as its client. Separating them is a violation.
• If the client is public, its protocol must be public so composition can supply an implementation.
• Composition layer(s) adapts concrete implementations to client-owned protocols.
• Modules MUST NOT know about CLI or each other.