Whether this attachment’s bytes are usable. ready is the only value a
send, a template save or a download accepts; anything else is why one of
those was refused. This read is never gated on it; it is where you look
up the answer.
Today’s values are ready, pending (bytes not stored yet) and failed
(they never will be). Everything POST /v1/attachments returns is ready
the moment it responds: the bytes are in the request. The other two exist
because an upload that mints an id BEFORE the bytes move cannot say that,
and the field is here now so that shape is not a second breaking response
change.
Modelled as a string rather than a closed union deliberately: the
set of values can grow (a content scanner adds a verdict of its own), and
a closed enum would make that addition the breaking change this field
exists to avoid. Branch on ready and treat every other value as
unusable-with-a-name; do not try to list them all.
