Fix gRPC auth: inject bearer token via PerRPCCredentials

The gRPC client was not sending the authorization header, causing
"missing authorization header" errors even when a token was configured.
Also fix config test to isolate from real ~/.config/mcrctl.toml.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cmd/mcrctl/client.go

@@ -62,10 +62,14 @@ func newClient(serverURL, grpcAddr, token, caCertFile string) (*apiClient, error
 
 	if grpcAddr != "" {
 		creds := credentials.NewTLS(tlsCfg)
-		cc, err := grpc.NewClient(grpcAddr,
+		dialOpts := []grpc.DialOption{
 			grpc.WithTransportCredentials(creds),
 			grpc.WithDefaultCallOptions(grpc.ForceCodecV2(mcrv1.JSONCodec{})),
-		)
+		}
+		if token != "" {
+			dialOpts = append(dialOpts, grpc.WithPerRPCCredentials(bearerToken(token)))
+		}
+		cc, err := grpc.NewClient(grpcAddr, dialOpts...)
 		if err != nil {
 			return nil, fmt.Errorf("grpc dial: %w", err)
 		}
@@ -91,6 +95,16 @@ func (c *apiClient) useGRPC() bool {
 	return c.grpcConn != nil
 }
 
+// bearerToken implements grpc.PerRPCCredentials, injecting the
+// Authorization header into every gRPC call.
+type bearerToken string
+
+func (t bearerToken) GetRequestMetadata(_ context.Context, _ ...string) (map[string]string, error) {
+	return map[string]string{"authorization": "Bearer " + string(t)}, nil
+}
+
+func (t bearerToken) RequireTransportSecurity() bool { return true }
+
 // apiError is the JSON error envelope returned by the REST API.
 type apiError struct {
 	Error string `json:"error"`

cmd/mcrctl/config_test.go

@@ -38,7 +38,9 @@ ca_cert = "/path/to/ca.pem"
 }
 
 func TestLoadConfigMissingDefaultIsOK(t *testing.T) {
-	// Empty path triggers default search; missing file is not an error.
+	// Point XDG_CONFIG_HOME at an empty dir so we don't find the real config.
+	t.Setenv("XDG_CONFIG_HOME", t.TempDir())
+
 	cfg, err := loadConfig("")
 	if err != nil {
 		t.Fatal(err)