Correlation scanner skips interpretation payloads — ScanStep claims every JSON surface and misses one

[thomas-stegemann]

Problem

RecordingCorrelationScanner.ScanStep documents itself as walking "every JSON-bearing surface of one step", but it misses one: the interpretations.

public static void ScanStep(BowireRecordingStep step, CorrelationLeafVisitor onLeaf)
{
    if (step is null) return;
    ScanLeaves(step.Body, onLeaf);
    foreach (var message in step.Messages) ScanLeaves(message, onLeaf);
    ScanLeaves(step.Response, onLeaf);
    if (step.SentMessages is not null)
        foreach (var frame in step.SentMessages) ScanFrame(frame, onLeaf);
    if (step.ReceivedMessages is not null)
        foreach (var frame in step.ReceivedMessages) ScanFrame(frame, onLeaf);
}

BowireRecordingStep.Interpretations and BowireRecordingFrame.Interpretations are both IList<RecordedInterpretation>?, and RecordedInterpretation.Payload is a JsonElement — a real JSON surface with real leaves, produced by the frame-semantics framework and carried verbatim through save/load. ScanFrame walks frame.Body and frame.Data but not frame.Interpretations.

Why it matters

An interpretation payload is where a semantic widget's data lives — a coordinate pair, a decoded identifier, a resolved entity reference. If a recording carries a correlation key only inside an interpretation payload, the correlated timeline cannot see it, and the step stays dark for no reason the user can observe.

Scope note

Found while shipping #545. It changes nothing for the harbor recording, which carries no interpretations, so it is not a regression in the timeline that ships today — it is a surface the scanner claims to cover and does not.

Acceptance

ScanStep walks step.Interpretations[].Payload, ScanFrame walks frame.Interpretations[].Payload, and a test builds a recording whose only shared identifier lives in an interpretation payload and asserts the two steps correlate.