Function build_report 

pub fn build_report(
    top: ContextObservation,
    iframe: ContextObservation,
    worker: ContextObservation,
    freshness: Option<FreshnessReport>,
) -> CoherenceDriftReport

Build a CoherenceDriftReport from three ContextObservations by running diff_surfaces for every applicable pair.

Skipped contexts are excluded from the comparison without raising an error or panic.