The FRWComponentsProbe module encodes flat FRW geometry with metric components gMetric and inverse gInv, coordinate derivatives pd, and Christoffel symbols Γ.
Probe 2 requires Γ¹₀₁ = ȧ a / a².
Γ_1_01 states:
Γ a 1 0 1 t = deriv a t * a t / (a t) ^ 2
Proof: simp [Γ, gInv, pd, Fin.sum_univ_four, deriv_a_sq a ha, gMetric_offdiag ...] followed by ring.
(The supplied slice contains no further simplification to ȧ/a, but the stated form matches the probe goal verbatim.)