V.T232 — Jet Collimation from Hoop Stress

Toroidal B_φ hoop stress P = B_φ²/(4πr) collimates jet. Equilibrium: sin(θ_jet) ≤ B_z/B_φ = ι_τ ≈ 0.341, recovering Jet Collimation Theorem from purely magnetic argument. Independent derivation of θ_jet ≤ 20°.