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

backend/internal/grpcsrv/collector/services.go

@@ -0,0 +1,38 @@
+package collector
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"gitea.d3m0k1d.ru/d3m0k1d/HellreigN/proto/proto"
+	"google.golang.org/grpc/metadata"
+)
+
+// ReportServices handles a unary service status update from an agent.
+// Agents send their current services list, which is stored in the collector.
+func (c *Collector) ReportServices(ctx context.Context, req *proto.ServicesUpdate) (*proto.ServicesUpdateResp, error) {
+	md, ok := metadata.FromIncomingContext(ctx)
+	if !ok {
+		return nil, fmt.Errorf("no metadata in context")
+	}
+
+	whoamiVals := md["whoami"]
+	if len(whoamiVals) == 0 {
+		return nil, fmt.Errorf("whoami metadata missing")
+	}
+	agentName := whoamiVals[0]
+
+	services := make([]Service, 0, len(req.Services))
+	for _, s := range req.Services {
+		services = append(services, Service{s.Name, s.Status})
+	}
+
+	if ok := c.tracker.UpdateServices(agentName, services); ok {
+		log.Printf("Updated services for agent %s: %v", agentName, services)
+	} else {
+		log.Printf("Warning: received services update for unknown agent %s", agentName)
+	}
+
+	return &proto.ServicesUpdateResp{}, nil
+}