X72-01: Pure-Continuous Energy Route

Opens the series and sets the Pure-Continuous experimental rules: discrete time steps, finite partitions as a core step, subsequences as a closure mechanism, and countable induction are all forbidden; only continuous time/space/scale, PDE/distributions, and Lebesgue/Sobolev/Lorentz-type continuous function spaces are allowed as tools, and the sole object of study is the maximal smooth solution generated by smooth, rapidly decaying initial data on R^3. Advances along the most direct, energy-first continuous closure route and proves two STOPs: STOP-C01 (a gap between the energy and the critical scaling — standard energy estimates cannot deliver critical control) and STOP-C02 (vortex stretching lacks coercivity — the pure-energy framework cannot see the sign structure of the stretching term). Together the two STOPs point to the next step: attack the scale-critical continuous carrier instead, handing off to the next round's Critical Continuous Carrier Route.