Representative parent cluster id per cluster (empty if the asset had none).
Per-cluster page of its children (empty if the asset had no groups).
Each page payload is independently gzip-compressed (decompress on fetch).
Byte length of the metadata region (header + resident block + TOC) = first page offset.
Header + always-resident block + TOC of a v3 asset — everything but the page geometry. Enough to drive streaming (page payloads are fetched by
byteOffset).