Constant LEAKAGE_CONDUCTANCE 

pub const LEAKAGE_CONDUCTANCE: f64 = 1e-12; // 9.9999999999999998E-13f64

Minimum conductance returned by nonlinear element derivative functions when a device is in cutoff or reverse-bias.

This is physically motivated: even in cutoff, real semiconductors have finite leakage current due to minority carriers and surface effects. For silicon: Icbo ≈ 1–100 nA → Gleakage ≈ 1e-12 to 1e-9 S. Using 1e-12 S (1 TΩ) is conservative and prevents Newton-Raphson from dividing by zero without adding measurable phantom current.