Function load_graph_or_exact_scan 

pub fn load_graph_or_exact_scan<'a>(
    reader: &'a SegmentReader,
    exact_request: ScanRequest<'_>,
    k: usize,
) -> Result<GraphLoadOutcome<'a>, GraphQueryError>

Loads a graph for a query, or loudly returns its typed error with exact results.

This is the single sanctioned recovery path for a corrupt derived accelerator. No other segment contract is downgraded to best-effort behavior.