Optionalanchoredset when the anchor was a locally validated header chain (headersync)
distinct independent sources supporting the header: the proof source (when known) plus each agreeing attester. 0 for checkpoint/sync anchors, which pin the header without live sources.
attesting sources whose hash-at-height matched the header
attesting sources queried (proof-building backend excluded)
Optionaltip
the header is pinned by a checkpoint, a synced chain, or enough independent sources