Update .gitignore and CMakeLists.txt; refine documentation in serial interface headers

- Added `.cache/` to `.gitignore` to exclude cache files from version control.
- Removed unnecessary whitespace in `CMakeLists.txt` for cleaner formatting.
- Clarified return value documentation in `serial_drain.h` and `serial_open.h` to improve understanding of function outcomes.

These changes enhance project organization and improve code documentation clarity.

Author: Katze719

.gitignore

@@ -1,4 +1,4 @@
 include/cpp_core/version.h
 build/
-
+.cache/
 

CMakeLists.txt

@@ -61,4 +61,4 @@ install(EXPORT cpp_coreTargets
 install(FILES
         ${CMAKE_CURRENT_BINARY_DIR}/cpp_coreConfig.cmake
         ${CMAKE_CURRENT_BINARY_DIR}/cpp_coreConfigVersion.cmake
-        DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/cpp_core) 
+        DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/cpp_core)

include/cpp_core/interface/serial_drain.h

@@ -29,7 +29,7 @@ extern "C"
      *
      * @param handle Port handle.
      * @param error_callback [optional] Callback to invoke on error. Defined in error_callback.h. Default is `nullptr`.
-     * @return 0 on success; negative ::cpp_core::StatusCodes value on error.
+     * @return 0 on success or a negative error code on failure.
      */
     MODULE_API auto serialDrain(
         int64_t        handle,

include/cpp_core/interface/serial_open.h

@@ -17,13 +17,13 @@ extern "C"
      *   - `const wchar_t*` on Windows.
      *
      * @param port Null-terminated device identifier (e.g. "COM3", "/dev/ttyUSB0"). Passing `nullptr` results in
-     * ::cpp_core::StatusCodes::kNotFoundError.
+     * a failure.
      * @param baudrate Desired baud rate in bit/s (≥ 300).
      * @param data_bits Number of data bits (5–8).
      * @param parity 0 = none, 1 = even, 2 = odd.
      * @param stop_bits 0 = 1 stop bit, 2 = 2 stop bits.
      * @param error_callback [optional] Callback to invoke on error. Defined in error_callback.h. Default is `nullptr`.
-     * @return A positive opaque handle on success or a negative value from ::cpp_core::StatusCodes on failure.
+     * @return A positive opaque handle on success or a negative value on failure.
      */
     MODULE_API auto serialOpen(
         void          *port,