Keep what a consumer gives up on until a person delivers it again or drops it

Design 25 promised a dead-letter stream that did not exist: a message a
consumer gave up on stayed only in its source, which drops it after a week,
and its condition cleared when the advisories stopped (hq issue 330, ADR 0264).

internal/broker/writers_test.go

@@ -30,6 +30,7 @@ var designRows = []string{
 	"a provider's standing",
 	"the operator-channel's open messages",
 	"the facts snapshot",
+	"a message a consumer gave up on",
 }
 
 func TestTheWritersTableIsTheDesigns(t *testing.T) {