Phase Transition at α = 1 (Stub)

@cite{zaslavsky-hu-levy-2020}

Formalizes Proposition 3 from @cite{zaslavsky-hu-levy-2020}: At α = 1, the RSA objective G_α equals the negative rate-distortion functional -R[D], connecting pragmatic reasoning to optimal compression.

Old RSAScenarioQ-based implementation removed; restate using RSAConfig.