A build says what it does on the bus, as it happens (novox/hq ADR 0157)

The build-machine seat emits `started` and `log.<build id>` beside `built`. Every line the builder
speaks — each step, each command with its duration, and on failure the command's own output — goes
to stderr as before and onto the bus under the build's id, one subject per build, kept a week in
EVENTS with every other event. `builds --log <id>` reads it back from the stream with a consumer
that is gone when the reading is done, on the command line and as the controller's seat verb;
`builds` lists each build's id and `build` says the id it asked with.

Lines are core publishes with a sequence number, so a build is not slowed by an ack per line and a
gap is visible; `started` and `built` are awaited into the stream. The seat protocol widens
additively at the controller's next start; the holder's grant follows on the broker node's next
composition.

cmd/mesh-builder/main.go

@@ -148,20 +148,34 @@ func answer(ctx context.Context, publisher builder.Publisher, on, workspace stri
 	// it either finishes or fails is indistinguishable from one that never arrived — which cost a long
 	// diagnosis against a running mesh, chasing "the handler never fired" when the truth was only that
 	// the handler said nothing until the end.
-	fmt.Fprintf(os.Stderr, "a build request arrived for %s\n", request.Repository)
+	fmt.Fprintf(os.Stderr, "a build request arrived for %s (%s)\n", request.Repository, request.ID)
+
+	// **Everything a build says goes two ways**: to stderr, as always, and onto the bus as the
+	// role's own events under the build's id (novox/hq ADR 0157) — so whoever asked, and anybody
+	// watching, reads the same lines this container's log holds, live, and after the fact from the
+	// stream. Said first, before anything runs, so a build that hangs is one that visibly started.
+	say := func(step, message string) {
+		fmt.Fprintf(os.Stderr, "  [%s] %s\n", step, message)
+		work.Say(step, message)
+	}
+	builder.Said = say
+	defer func() { builder.Said = nil }()
+	if err := work.Began(ctx); err != nil {
+		fmt.Fprintf(os.Stderr, "cannot say a build started: %v\n", err)
+	}
 
 	result := link.BuildResult{
 		ID: request.ID, Repository: request.Repository, Path: request.Path,
 		Ref: request.Ref, On: on,
 	}
-	fmt.Fprintf(os.Stderr, "building %s", request.Repository)
+	what := "building " + request.Repository
 	if request.Path != "" {
-		fmt.Fprintf(os.Stderr, " at %s", request.Path)
+		what += " at " + request.Path
 	}
 	if request.Ref != "" {
-		fmt.Fprintf(os.Stderr, " at %s", request.Ref)
+		what += " on " + request.Ref
 	}
-	fmt.Fprintln(os.Stderr)
+	say("build", what)
 
 	npmrc, err := packagesFrom()
 	var built builder.Result
@@ -171,15 +185,13 @@ func answer(ctx context.Context, publisher builder.Publisher, on, workspace stri
 		// after a clone that then fails at npm ci.
 		built, err = builder.Build(ctx, builder.Command, publisher,
 			request.Repository, request.Path, request.Ref, workspace, request.Held, npmrc,
-			forgeFrom(), func(step, message string) {
-				fmt.Fprintf(os.Stderr, "  [%s] %s\n", step, message)
-			}, request.Seats)
+			forgeFrom(), say, request.Seats)
 	}
 	if err != nil {
 		// A failure is a result. A build that fails and says nothing is indistinguishable from a
 		// builder that is not running, and those want completely different responses.
 		result.Failed = err.Error()
-		fmt.Fprintf(os.Stderr, "  failed: %v\n", err)
+		say("failed", err.Error())
 	} else {
 		manifest, marshalErr := json.Marshal(built.Manifest)
 		if marshalErr != nil {
@@ -196,7 +208,7 @@ func answer(ctx context.Context, publisher builder.Publisher, on, workspace stri
 			for _, r := range built.Read {
 				result.Read = append(result.Read, link.ReadRepository{Repository: r.Repository, Ref: r.Ref})
 			}
-			fmt.Fprintf(os.Stderr, "  built %s from %s\n", built.Manifest.Module, short(built.Commit))
+			say("built", built.Manifest.Module+" from "+short(built.Commit))
 		}
 	}