Review caught a real gap: action='update' also accepts deliver, and the
tool description explicitly steers agents toward update-over-create — so
a cron-context agent updating a job to deliver='origin' would recreate
exactly the dangling literal-origin shape the create-path resolution
prevents (stored 'origin' on an origin-less job → fire-time home-channel
guessing or silent drop).
Wrap the update site in the same resolver. Semantics follow the create
precedent: in cron context, 'origin' means 'my run's target', resolved
concretely at mutation time; outside cron context updates are
byte-identical to before.
