A resource attached in a save now ignores any sponsor recorded for it
before it was removed: the caller must be able to sponsor it and confirm.
YAML import prunes the sponsors of resources it drops, for agents and
workflow graphs. Sponsor details, with the resources' names, go only to
people who may edit the agent. The workflow read returns the names of
every node tool and source, so editors can remove the owner's private
ones. An agent image is stored only once the save is known to go ahead.
Sponsoring a tool, source or prompt the agent's owner can't use now takes
owning it or having edit access to it; use access alone no longer extends it
to the agent's audience. A save that would make the caller a new sponsor is
refused with 409 sponsor_confirmation_required (the resources and the
agent's audience) until it is retried with confirm_sponsor listing them.
When a sponsor loses access, the resource stops instead of passing to
whoever saves next; another editor takes it over only by confirming.
Workflows follow the same rules. sponsor_details now reports each
sponsorship's state, the reason it stopped, and whether the reader can
take it over.
arc53-machine