Crossover Masses by Carrier: Which Branch Sets the Smallest Possible Black Hole

The electron branch gives a crossover of 1.592e+14 kilograms, the proton branch 8.671e+10 kilograms, and the neutron branch 8.659e+10 kilograms. The electron-to-neutron ratio is 1.839e+03, matching the inverse mass ratio as the scaling law requires. The practical consequence is sharp: had a light carrier set the operative bound, the smallest holes would be heavier by three orders of magnitude and evaporation endpoints would sit in a different observational regime entirely. Carrier choice is thus not a footnote to remnant physics but its largest single lever, larger than the prescription coefficient's factor of two. Computed from stated assumptions, not measured.