Fix ESP-NOW unicast by using sender MAC in client registry.

Register slaves from recv src_addr instead of protobuf mac bytes, add
ESPNOW_UNICAST_TEST for path verification, restore unicast deadzone, and
expose unicast-test in goTool.

Co-authored-by: Cursor <cursoragent@cursor.com>

main/CMakeLists.txt

@@ -17,6 +17,7 @@ idf_component_register(
   "cmd_version.c"
   "cmd_client_info.c"
   "cmd_accel_deadzone.c"
+  "cmd_espnow_unicast_test.c"
   "client_registry.c"
   "esp_now_comm.c"
   "esp_now_proto.c"