Function run_detector 

pub fn run_detector(
    detector: &dyn ChangePointDetector,
    motif: MotifClass,
    stream: &ResidualStream,
) -> Vec<Episode>

Run a detector against one motif of a residual stream and emit Episodes that the standard metrics path can score.

The series is built per-channel: for each distinct channel string under the motif’s residual class we invoke detector.detect independently, then union the resulting change-points. This mirrors the channel granularity the dsfb motif state machine gets for free — without it the baseline would be unfairly starved of the channel signal that the motif grammar consumes.