Function export_hmm_viterbi_trace 

pub fn export_hmm_viterbi_trace<P: AsRef<Path>>(
    debug_info: &DebugInfo,
    output_path: P,
) -> Result<(), ProjectionError>

Export Phase 3 – Viterbi decoding trace as GeoJSON

Produces a FeatureCollection with one LineString feature per HMM decoding step (one per GNSS observation), linking the raw GNSS point to the projected point on the netelement chosen by the Viterbi algorithm at that step. Features with no matching candidate are emitted with null geometry so they still appear in attribute tables.

Properties per feature:

• step – observation index (0-based)
• netelement_id – the netelement chosen at this step
• decision_type – type of Viterbi event ("viterbi_init" or "viterbi_transition")
• selected_probability – emission probability of the chosen candidate (when available)
• alternatives_count – number of alternatives considered
• reason – human-readable selection rationale