A.11.OP:4.6 - Keep framework layers distinct

FPF owns this cross-domain admission principle. A Method Engineering DPF may use it when deciding which requirements should be mandatory in a named Method situation; that DPF still owns the Method-specific design. A local practice framework may bind the principle to its own execution and assurance mechanisms. Those mechanisms retain local scope, and the FPF admission condition must still be established for the declared use.