A-248: buildrun.Asker puts under the asker its subject names

The indexer's validation ask rides accept.<queue>.<asker> under its own
name (§712, A-232); an asker that names none still puts under the builder's.

Builds: design 47 G A-248, A-247, §712

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

modules/mesh-delivery-builder/buildrun/asks.go

@@ -1,6 +1,7 @@
 package buildrun
 
 import (
+	"cmp"
 	"context"
 	"encoding/json"
 	"errors"
@@ -34,6 +35,9 @@ type AskWaiter interface {
 
 // Asker puts asks and waits for their steps.
 type Asker struct {
+	// Name is the asker the subject names, the caller's seat name (design 47 G A-248, A-163): empty puts under the builder's
+	// name until the asker rename after the join.
+	Name      string
 	Publisher AskPublisher
 	Waiter    AskWaiter
 	// Seats finds the build module of an ask's language (design 47 G A-82).
@@ -173,8 +177,8 @@ func (k Asker) dropped(a buildstep.StepAsk, why string) {
 // PutTry is how long one publish of an ask waits for its stream's answer before it is made again (Put).
 var PutTry = 10 * time.Second
 
-// Put puts a on its stream: the seat's accept subject of its language and kind, under the builder's name as asker (design 47 G
-// §481, §600: `accept.<queue>.builder`). The put is a kept call (novox/hq ADR 0668
+// Put puts a on its stream: the seat's accept subject of its language and kind, under the asker's Name, else the builder's
+// name (design 47 G §481, §600, A-248: `accept.<queue>.builder`). The put is a kept call (novox/hq ADR 0668
 // §1, §2; issue 1966, issue 1748 note 27): it carries the ask's id as its message id, so the stream takes it once, and it
 // is made again through every transport fault (a deadline, no responders) within busretry.Bound, each try bounded by
 // PutTry, until ctx ends. A put that still meets one is an error opening `transport fault:` (TransportFault), so the key it
@@ -184,7 +188,7 @@ func (k Asker) Put(ctx context.Context, a buildstep.StepAsk) error {
 	if err != nil {
 		return err
 	}
-	subject, err := buildstep.AskSubjectBy(a.Language, a.Kind, buildstep.AskerBuilder)
+	subject, err := buildstep.AskSubjectBy(a.Language, a.Kind, cmp.Or(k.Name, buildstep.AskerBuilder))
 	if err != nil {
 		return err
 	}

modules/mesh-delivery-builder/buildrun/asks_test.go

@@ -44,6 +44,11 @@ func TestAnAskerPutsOnceAndReadsTheStep(t *testing.T) {
 	if len(subjects.seen) != 1 || subjects.seen[0] != "mesh.seat.node-build-go.accept."+goAsk("x").Kind+".builder" {
 		t.Fatalf("the ask was put on %v", subjects.seen)
 	}
+	// A-248: an asker that names itself puts under its own name.
+	byName := Asker{Name: "indexer", Seats: testSeats(), Publisher: subjects, Waiter: f}
+	if err := byName.Put(context.Background(), goAsk("mvl0frv18d1959")); err != nil || subjects.seen[len(subjects.seen)-1] != "mesh.seat.node-build-go.accept."+goAsk("x").Kind+".indexer" {
+		t.Fatalf("a named asker put on %v (%v)", subjects.seen, err)
+	}
 	f.Answer = func(a buildstep.StepAsk) buildstep.Step {
 		return buildstep.Step{ID: a.ID, Node: "shanks", State: buildstep.StepRefused, Reason: "go 1.27 installed"}
 	}