Serve the node-engine verb composition: a module's composition beside what runs, its judgement and its diff (issue 774)

Four providers waited for a yes on 2026-10-31 and nobody could read what waited: the have said only
"where its data is kept". The read verb composition answers it from the engine: the latest revision of the
want's build or the one asked by digest, every revision the bucket keeps, what runs and where that is known from,
the want and the have, the move's judgement and whether it waits for a yes, and with diff the resources that
differ, a received file naming its consumers. revisionNamed now reads the same revisions.

cmd/mesh-host/engineseat.go

@@ -275,3 +275,20 @@ func reconcileActs(ctx context.Context, h *link.HandActs) {
 		}
 	}
 }
+
+// compositionReadFor bounds one read of the verb composition: the revisions of one key from the bucket.
+const compositionReadFor = 20 * time.Second
+
+// compositionFrom answers the verb composition from the node agent that runs now (issue 774); refused in words while
+// none does.
+func compositionFrom(current *agentNow) func(module, digest string, diff bool) (any, error) {
+	return func(module, digest string, diff bool) (any, error) {
+		ag := current.get()
+		if ag == nil {
+			return nil, errors.New("this engine's node agent has not started, so it holds no composition yet")
+		}
+		ctx, cancel := context.WithTimeout(context.Background(), compositionReadFor)
+		defer cancel()
+		return ag.Composition(ctx, module, digest, diff)
+	}
+}

cmd/mesh-host/main.go

@@ -1141,6 +1141,7 @@ func runLink(ctx context.Context, opts options) error {
 	queue.Acts = engineActs(opts, mine.Node, queue, setuidSearch)
 	go reconcileActs(ctx, queue.Acts)
 	current := &agentNow{}
+	queue.Acts.Composition = compositionFrom(current)
 	setRunsHere(runsFromAgent(current))
 	factsOfNow := func(ctx context.Context, ag *agent.Agent) {
 		sayFacts(ctx, opts, mine.Membership.Signer, queue, say, ag)