DCRP-28: Type-II Double-Level Crossing and the Genuine Euler Barrier

Isolates the genuine two-level energy transition, separates the surviving viscous payment from the genuinely inviscid Type-II limit, proves that a finite Euler-time level crossing cannot become a silent Euler/Euler–Reynolds profile, and shows that no known general finite-energy Euler Liouville theorem can close the remaining branch.