DLV-F5r (indexer's case): the assigner's runtime answering after the indexer asked is followed within the bound

A case of the indexer's existing whole-module test: the assigner's first view is held until the
indexer has started, and only the placed node's toolchain counts once it answers (ADR 0621 §3).

Claude-Session: https://claude.ai/code/session_01JG73KJNrH5EgFXMKKYSrig

modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/integration_test.go

@@ -721,6 +721,11 @@ func TestIndexerCountsOnlyThePlacedBuildNodesToolchains(t *testing.T) {
 			t.Fatal(err)
 		}
 	}
+	// DLV-F5r (ADR 0621 §3): the assigner's runtime starts together with the indexer and answers its first view only after
+	// the indexer asked; within the bound the indexer follows the placement it answers (only n1's toolchain counts).
+	up := make(chan struct{})
+	assignerLate = up
+	t.Cleanup(func() { assignerLate = nil })
 	js, ctx, _, modules := startIndexer(t, func(context.Context, buildLog) {}, func(ctx context.Context, js jetstream.JetStream) {
 		kv, err := js.CreateKeyValue(ctx, jetstream.KeyValueConfig{Bucket: delivery.ToolchainsBucket("mesh-build-go"), History: 1})
 		if err != nil {
@@ -744,6 +749,7 @@ func TestIndexerCountsOnlyThePlacedBuildNodesToolchains(t *testing.T) {
 		place(ctx, t, "n1", "mesh-build-go")
 		place(ctx, t, "n2")
 	})
+	close(up)
 	data, err := delivery.EncodeForge(delivery.Forge{Kind: delivery.ForgeMerged, Repository: "novox/mesh-catalog", Branch: "feat/x", Number: 302,
 		Head: "0123456789abcdef0123456789abcdef01234567", Merge: "89abcdef0123456789abcdef0123456789abcdef", Root: "r0",
 		Trees:     map[string]string{"modules/avahi": "newtree"},
@@ -809,6 +815,10 @@ func TestIndexerCountsOnlyThePlacedBuildNodesToolchains(t *testing.T) {
 	}
 }
 
+// assignerLate, when set before startIndexer, holds every answer of the assigner's first view until it is closed: the
+// assigner's runtime started together with the indexer's, answering after the indexer asked (DLV-F5r).
+var assignerLate chan struct{}
+
 // serveAssignerPlacement is the assigner as the owner of its placement (ADR 0615, ADR 0621), with the real owner's side:
 // its first-view tool placement answered from the bucket at its mark (the bucket made empty where a test made none),
 // and its views family said by the views emitter onto ASSIGNER_VIEWS, which the indexer's durable consumer reads.
@@ -835,7 +845,15 @@ func serveAssignerPlacement(t *testing.T, ctx context.Context, js jetstream.JetS
 	if err := em.Start(ctx, delivery.PlacementState, placement, nil); err != nil {
 		t.Fatal(err)
 	}
+	late := assignerLate
 	sub, err := nc.Subscribe("mesh.mod.mesh-delivery-assigner.call.placement.>", func(m *nats.Msg) {
+		if late != nil { // its runtime comes up after the indexer started (DLV-F5r)
+			select {
+			case <-late:
+			case <-ctx.Done():
+				return
+			}
+		}
 		a, err := views.FirstView(delivery.AssignerModule, delivery.PlacementState, jsSource{ctx, placement}, jsSource{ctx, marks}, "", time.Now())
 		out := map[string]any{"result": a, "node": "n0"}
 		if err != nil {