feat: big ahh commit

- agent+proto+backend: transfer service status
- agent: fix returning empty message on nonzero exit status
- backend: refactor collector+commander and handlers dependent on them: implement agent accounting via grpc stats handler

agent/main.go

@@ -22,6 +22,7 @@ import (
 	"github.com/samber/lo"
 	"golang.org/x/sync/errgroup"
 	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials"
 	"google.golang.org/grpc/metadata"
 )
 
@@ -110,6 +111,13 @@ func main() {
 		return ccli.HandleCommands(ctx, grpcAddr, creds)
 	})
 
+	// Start services update stream
+	if len(cfg.Services) > 0 {
+		wg.Go(func() error {
+			return reportServices(ctx, grpcAddr, creds, cfg.Label, cfg.Services, lgr)
+		})
+	}
+
 	// Start log collectors
 	if len(cfg.Services) > 0 {
 		wg.Go(func() error {
@@ -301,3 +309,52 @@ func reconnectStream(
 
 	return fmt.Errorf("failed to reconnect after 5 attempts for service %s", service)
 }
+
+// reportServices periodically sends service status updates to the backend via gRPC.
+// For now, all configured services are reported as "up" every 5 seconds.
+func reportServices(
+	ctx context.Context,
+	grpcAddr string,
+	creds credentials.TransportCredentials,
+	label string,
+	services []config.ServiceConfig,
+	lgr *logger.Logger,
+) error {
+	conn, err := grpc.NewClient(grpcAddr, grpc.WithTransportCredentials(creds))
+	if err != nil {
+		return fmt.Errorf("failed to connect for services report: %w", err)
+	}
+	defer conn.Close()
+
+	ccli := proto.NewCollectorClient(conn)
+	ticker := time.NewTicker(5 * time.Second)
+	defer ticker.Stop()
+
+	// Send immediately on start, then every 5 seconds
+	for {
+		svcUpdates := make([]*proto.ServicesUpdate_ServiceUpdate, 0, len(services))
+		for _, svc := range services {
+			svcUpdates = append(svcUpdates, &proto.ServicesUpdate_ServiceUpdate{
+				Name:   svc.Name,
+				Status: "up",
+			})
+		}
+
+		md := metadata.New(map[string]string{"whoami": label})
+		_, err := ccli.ReportServices(
+			metadata.NewOutgoingContext(ctx, md),
+			&proto.ServicesUpdate{Services: svcUpdates},
+		)
+		if err != nil {
+			lgr.Warn("Failed to report services", "err", err)
+		} else {
+			lgr.Debug("Services reported successfully", "count", len(services))
+		}
+
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		case <-ticker.C:
+		}
+	}
+}