Function get_input_method 

pub fn get_input_method() -> Result<String, ImSwitchError>

Returns the current input method identifier.

The returned value is platform-dependent:

• Windows: Keyboard layout ID (KLID), e.g., "00000409"
• macOS: Input source identifier, e.g., "com.apple.keylayout.ABC"
• Linux: Input method name (IM framework-dependent)