Let failed join the seat optional, and let a seeded row carry both changes

failed was required, so the controller refused the systemd module running
today and the module serving it was refused by the controller running
today: neither could land first. It is now optional (Verb.Optional, #117).

Two things kept either change from reaching a mesh whose seat rows already
exist: re-seeding added a verb but never an argument to one, and the
console refuses an argument the row does not name, so the journal window
would stay unreachable; and the optional mark is never stored, so a verb
seeded into a row came back required. A row's verb now gains the arguments
the binary names, and the working set takes the optional mark from the
compiled seat, which also keeps mesh-delivery's checks optional once seeded.

cmd/mesh-controller/seat_dependencies_test.go

@@ -15,7 +15,7 @@ import (
 func serviceManagerHolder() catalogue.Manifest {
 	return catalogue.Manifest{Module: "systemd", Version: "1",
 		Claims: []catalogue.Claim{{Name: catalogue.ServiceManagerSeat, Scope: catalogue.ScopeNode,
-			Serves: []string{"units", "status", "start", "stop", "restart", "enable", "disable", "journal", "failed"}}},
+			Serves: []string{"units", "status", "start", "stop", "restart", "enable", "disable", "journal"}}},
 		Resources: []map[string]any{{"id": "systemd", "type": "package", "package": "systemd"}}}
 }