* fix(system): keep a restore review's upload form alive until it is answered (#583)
WebKit can read a FormData's file part after fetch() returned, and with a
request interceptor armed it does. uploadRestore held its FormData only in a
local that was dead after the call, so a garbage collection in between dropped
the form and the server got an empty file ("Uploaded file is empty"); the
Restore preview never opened. The page now holds each upload's form until the
upload is answered.
* docs(system): say what the #583 regression spec proves in each browser (#583)
Vito
cb94b12c1b