Area 2 (join 11): the order-wait fixture's machine is online again

The five §298 order-wait tests of b2l (A-245, A-258, A-259, A-260) held no
wait and said none after the merge with b2f: b2l's fixture put ace's presence
as online (presenceValue(true)), and the merge rewrote it as b2f's
heardPresence("ace", true, ...), whose flag says away. With every node away
no module had a canary, so no want moved and no order edge was held (an order
wait starts only on an online node, §268). The fixture now hears ace back;
the order waits are built as those answers have them, unchanged.

Builds: design 47 G lead answers A-245, A-258, A-259, A-260 (join 11 area 2)

Claude-Session: https://claude.ai/code/session_01NcbgfGKaxw984XyAPfLm4h

modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/orderwaits_test.go

@@ -108,7 +108,7 @@ func newOrderFixture(t *testing.T, mods []orderMod, history ...map[string]string
 	for key, raw := range values {
 		p.w.put(plc.AssignmentsBucket, key, raw)
 	}
-	p.w.heardPresence("ace", true, time.Now())
+	p.w.heardPresence("ace", false, time.Now()) // ace is online: its last presence event heard is machine-back
 	objects := memObjects{}
 	for i, at := range history {
 		half := meshcatalogclient.Half{Revision: meshcatalog.CatalogRevision{Branch: trunkBranch, Kind: "trunk", Revision: int64(i + 1), Source: int64(i + 1)},