cross-model-instruction-authoring

Use when creating, revising, or adapting Agent Skills, custom agent prompts, subagent instructions, or instruction packages that should work across multiple models or runtimes, especially smaller/faster and frontier GPT/Claude models. Produces a model-neutral core, separates runtime-specific adapters, and checks both small-model executability and frontier-model overconstraint. Do not use for a review-only audit when no authored or revised artifact is requested.