Function evaluate_phase_statuses 

pub fn evaluate_phase_statuses(
    records: &[PhaseStatusV1],
    partitions: NonZero<usize>,
    step: CollectiveStepV1,
) -> Result<(), Diagnostic>

Require one ready status per partition in exact rank order.

The diagnostic for a common rejection is selected by the lowest rejected partition, so every rank presented with the same records returns the same stable result.

Errors

Returns EQ0807 for record-count, phase, iteration, or rank-order drift, or the selected common diagnostic for a rejected rank.