Go build module: the compose test gives its module a slot, since a node with no capacity set now pulls nothing (issue 1126, ADR 0567 §15)

The test built its module with no settings file and no Capacity; the new
buildstep.NodeCapacity answers 0 for that (no default names a node), so the
puller took no ask and the test timed out after 90 s in check 205f634c30df.
Failed first locally at origin/main af89893d (90.1 s), passes with the slot (2.5 s).

modules/mesh-build-go/cmd/mesh-build-go/compose_integration_test.go

@@ -73,6 +73,7 @@ func TestAComposeAskIsBuiltOnceAndAnsweredOnTheBus(t *testing.T) {
 	states := newStates()
 	m := moduleWith(states, "go1.26.0")
 	m.Work, m.Cache, m.Inside = t.TempDir(), t.TempDir(), true
+	m.Capacity = func() int { return 1 } // its own slot: no settings file, and a node with no capacity set pulls nothing (ADR 0567 §15)
 	m.Run = StepRunner(t.TempDir())
 	m.GoModCache = goEnvOf(t, "GOMODCACHE")      // the module cache this module's own build filled, read and not fetched
 	run, gocache := m.Run, goEnvOf(t, "GOCACHE") // this machine's build cache, so the composer's packages compile once