Function global_test 

pub fn global_test(
    residuals: &[FloatResidual],
    n_states: usize,
    config: RaimConfig,
) -> Result<RaimResult, RaimError>

Run the PPP RAIM global chi-square test over post-fit float residual rows.

Each FloatResidual contributes one code residual and one phase residual, so n_obs is twice residuals.len(). The residual row weights are treated as inverse-sigma solver weights, then divided by RaimConfig::measurement_sigma_m before accumulating the SSE.