Offer no Replay for a delivery to a deleted target (closes #387)

The event log offered Replay on a delivery whose target was deleted,
and the refusal told the operator to recreate the target and replay.
That cannot work: a recreated target is a new one the old delivery
does not name, so the replay is refused again. The Replay button is
now left off such a delivery, whose row already names the target as
deleted, and the refusal a page left open can still reach now points
to Resubmit, which sends the event to the webhook's currently active
targets.

Model: opus-5-5

README.md

@@ -1856,7 +1856,11 @@ deliver where the destination has since been fixed. A target that has
 been deleted or deactivated therefore refuses the replay with a
 message on the event log rather than delivering from stale
 configuration, and a replay is refused while an earlier one for the
-same event and target is still pending or retrying.
+same event and target is still pending or retrying. A delivery whose
+target has been deleted shows no **Replay** action at all: recreating
+the target makes a new one that the old delivery does not name, so
+**Resubmit** is how that event reaches the webhook's currently active
+targets.
 
 **Resubmit.** Replay recovers one delivery; **resubmit** re-injects one
 EVENT. The event log offers a per-event **Resubmit** action that stores