OptionalabsoluteThe source's absolute path or URL, if known — recorded as the workbook's origin.
OptionalcanWhether the acquired source can be written back to (a silent re-save). Only the store knows —
e.g. a local fs path can (Node), a browser File can only when the store holds a writable
handle for it. Defaults to false when omitted; seeds the minted origin's
IWorkbookIO.Origin.canWrite.
OptionalextFile extension derived from the source name, used for format detection.
OptionalformatExplicit format hint (extension, MIME type, or key), if any.
OptionallastWhen the source was last modified, in milliseconds since the epoch, if known.
OptionalnameThe source's display name (without path), if known.
OptionalsizeThe source size in bytes, if known.
OptionalsourceThe detected source type (e.g. 'file', 'fetch'), used for a fallback display name.
What a IWorkbookIO.IBackingStore knows about an acquired source, passed to ReadRequest.decode.