Marker module for per-call demo resolution strategies. v1 ships a single strategy (Dsxir.DemoStrategy.KNN); the runtime hook in Dsxir.Module.Runtime.call/4 dispatches via a case over the struct.

A future @behaviour Dsxir.DemoStrategy with resolve/3 is the natural generalization when a second concrete strategy lands (MMR, rerank). v1 keeps it as a struct union per the design.