de Broglie velocity ratio: λ(2v)/λ(v) = 1/2

Sympy-exact witness of the de Broglie wavelength-velocity inverse proportionality. Setup: λ = h/(m_n·v). Identity: doubling v halves λ — λ(2v)/λ(v) = 1/2 — a rational identity independent of h, m_n. Oracle pins: lam_sym = 'h/(m_n*v)'…