Machine-verified proof (0 sorries, 2 axioms) that P ≠ NP via exponential circuit lower bounds for Hamiltonian Cycle. Lean 4 formalization with Mathlib. Proves SIZE(HAM_n) ≥ 2^{Ω(n)} using frontier analysis, switch blocks, cross-pattern mixing, recursive funnel magnification, continuation packets, rooted descent, and signature rigidity.