type WKBResult struct {
Geometry map[string]any SRIDs []uint32}
WKBResult contains a decoded GeoJSON-shaped geometry and every EWKB SRID
encountered in its top-level or nested geometry headers. Plain OGC/ISO WKB
has no embedded SRID and leaves SRIDs empty.
DecodeWKB decodes OGC WKB, EWKB flags, and ISO SQL/MM Z/M/ZM type offsets.
Z is preserved and M is consumed but dropped because GeoJSON has no measure
ordinate.