Add HWT905-RS232 IMU reader (Phase 1: observation only, no ROS)

Standalone C++/termios serial reader for the WitMotion HWT905 IMU
(9600bps active-push protocol), printing accel/gyro/angle to stdout
with optional CSV logging.

CMakeLists.txt

@@ -0,0 +1,13 @@
+cmake_minimum_required(VERSION 3.10)
+project(duru_imu_ws CXX)
+
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+if(NOT CMAKE_BUILD_TYPE)
+  set(CMAKE_BUILD_TYPE Release)
+endif()
+
+add_compile_options(-Wall -Wextra)
+
+add_executable(imu_reader src/main.cpp)