Function evaluate_gate 

pub fn evaluate_gate(
    hard_pass: bool,
    candidate_v: f64,
    best_accepted_v: f64,
    rho_gate: f64,
) -> Result<GateDecision>

Evaluate the measured acceptance gate for a candidate.

• hard_pass — all required verifiers and hard policy constraints passed.
• candidate_v — the candidate’s total energy V(y).
• best_accepted_v — the best accepted energy V(x_best) so far.
• rho_gate — the single descent tolerance (> 0).