[client] Add non default socket file discovery (#5425)

- Automatic Unix daemon address discovery: if the default socket is missing, the client can find and use a single available socket.
- Client startup now resolves daemon addresses more robustly while preserving non-Unix behavior.

client/cmd/root.go

@@ -22,6 +22,7 @@ import (
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials/insecure"
 
+	daddr "github.com/netbirdio/netbird/client/internal/daemonaddr"
 	"github.com/netbirdio/netbird/client/internal/profilemanager"
 )
 
@@ -80,6 +81,15 @@ var (
 		Short:        "",
 		Long:         "",
 		SilenceUsage: true,
+		PersistentPreRunE: func(cmd *cobra.Command, args []string) error {
+			SetFlagsFromEnvVars(cmd.Root())
+
+			// Don't resolve for service commands — they create the socket, not connect to it.
+			if !isServiceCmd(cmd) {
+				daemonAddr = daddr.ResolveUnixDaemonAddr(daemonAddr)
+			}
+			return nil
+		},
 	}
 )
 
@@ -386,7 +396,6 @@ func migrateToNetbird(oldPath, newPath string) bool {
 }
 
 func getClient(cmd *cobra.Command) (*grpc.ClientConn, error) {
-	SetFlagsFromEnvVars(rootCmd)
 	cmd.SetOut(cmd.OutOrStdout())
 
 	conn, err := DialClientGRPCServer(cmd.Context(), daemonAddr)
@@ -399,3 +408,13 @@ func getClient(cmd *cobra.Command) (*grpc.ClientConn, error) {
 
 	return conn, nil
 }
+
+// isServiceCmd returns true if cmd is the "service" command or a child of it.
+func isServiceCmd(cmd *cobra.Command) bool {
+	for c := cmd; c != nil; c = c.Parent() {
+		if c.Name() == "service" {
+			return true
+		}
+	}
+	return false
+}