X72-34: Cancellation-Budget Dynamics

Picks up Round 33's accounting framework that splits signed sources into net, total variation, and cancellation coefficient (STOP-C37), and studies the evolution of the cancellation reserve itself. Proves that diffusion only erodes the reserve (the Kato Equal-Removal Law), so sustained cancellation must be continually replenished from the minority-sign side. For determinant sources, the nonnegative vorticity-stretching term in the net-positive dangerous branch likewise drains the negative reserve, and genuine replenishment can only come from the pressure and tensor-diffusion curvature channels; for the renormalized pair source, replenishment comes from the source's second-order difference and the transport commutator. STOP-C38 (Cancellation-Reserve/Sign-Selective Replenishment Gap) hands to the next round the task of auditing whether these replenishment channels are free resources.