Function execute_command 

pub fn execute_command(
    command_text: &str,
    cwd: Option<&Path>,
) -> Result<ExecutionResult>

Execute a command string through the shell.

Uses the SHELL environment variable (fallback /bin/sh) to run the command via sh -c. Stdin, stdout, and stderr are inherited so the user sees output in real-time and can interact with prompts.

If cwd is provided and the directory exists, the command runs in that directory. If the directory doesn’t exist, a warning is printed to stderr and the current directory is used instead.

For simple cd <path> commands, returns the resolved new directory in ExecutionResult::new_cwd so the caller can update its working directory for subsequent commands.

Errors

Returns an error if the shell process cannot be spawned or waited on.