Function apply_anchors 

pub fn apply_anchors(
    anchors: &[ResolvedAnchor],
    position_candidates: &mut [Vec<CandidateNetElement>],
    emission_probs: &mut [Vec<f64>],
    netelements: &[Netelement],
    netelement_index: &HashMap<String, usize>,
    gnss_index_map: Option<&[usize]>,
) -> Result<(), DetectionError>

Apply every anchor to position_candidates / emission_probs.

gnss_index_map (when Some) maps the anchor’s original GNSS index (referring to the input GNSS array) to the working index (after resampling). When None, anchors are assumed to use working indices directly.

Out-of-bounds anchors (gnss_index >= position_candidates.len()) are silently skipped — the caller’s filter pass should already have removed them, but defensive checks keep us robust against resampling edge cases.