Carry a held merge's new announcement into its record (issue 1173)

HoldMerge replaced the event on the flag only; the record kept the old one.

internal/inventory/chain_rollouts.go

@@ -634,6 +634,10 @@ func (e *recordEdit) apply(held []chain.HeldMerge) []chain.HeldMerge {
 		}
 		if f, has := e.flag[k]; has {
 			h.Waiting, h.Alone = f.Waiting, f.Alone
+			// A merge put back to waiting may carry a new announcement (HoldMerge); every other flag copies its own.
+			if len(f.Event) > 0 {
+				h.Event = f.Event
+			}
 		}
 		out = append(out, h)
 	}