Add exact-task named HardNet control audit

Add exact Theorem 3.5 bound audit

Reproduce claim 4 safety-critical control: CAffNet CBF projection 100% safe + reaches goal (margin >=0), soft baseline collides every run (margin -0.10)

Reproduce CAffNet Thm 3.4/3.5: exact affine constraint satisfaction (2e-15 equality, 0 inequality) + universal approx (RMSE 0.0139->0.0048 as width grows)