PASS nonlinear area-energy derivative agrees with independent finite difference PASS nonlinear pressure Hessian agrees with independent finite difference PASS variational equilibrium has the radius-derived constant Laplace pressure PASS localized trial/test spaces are biorthogonal and retain boundary coenergy traces PASS each region volume is an exact invariant direction of the projection PASS full nonlinear coupled step preserves regional volumes with shared flux PASS pressure plus explicit capillary shape work closes both regional energy budgets PASS regional capillary-energy split independently matches the explicit shape-work formula PASS localized reduced step preserves separate volume and interface-power ledgers PASS unreduced two-block coordinate control matches the full physical solve PASS reference-perturbation pressure agrees with extended-precision difference for weak states PASS weak-drive fine-grid step and regional power budget converge without tolerance changes 12 passed, 0 failed