…r handling

Introduce a new `write_stdout_line` function that locks stdout and returns a Result to handle write failures gracefully. Replace all `println!` calls in verbose output, debug messages, and path printing with this function, propagating errors via `CopyResult<()>` instead of panicking on I/O errors. This improves reliability when stdout is closed or encounters issues during cp operations.

…justing exit code

- Made `code` mutable to allow modification on flush errors.
- Ignore BrokenPipe errors during stdout flush to avoid breaking utilities that silence it (e.g., seq).
- Set exit code to 1 if a flush error occurs and the original code was 0, treating write errors as failures.

- Added check to capture if stdout was closed before utility execution using fcntl on Unix.
- Modified flush error handling to ignore EBADF errors when stdout was pre-closed, avoiding false failures for silent commands.

Reorder imports for consistency and refactor the ignore_closed_stdout condition to a more concise form, improving code readability without altering functionality.

Implement mechanism to detect if stdout was closed at process start and track write attempts. Add `check_stdout_write()` to error on writes when stdout is closed, preventing issues in utilities like cp and printf. Use `TrackingWriter` in printf for write monitoring. This improves robustness in scenarios like pipeline redirections or closed stdout.

…lity

- Condensed multi-line cfg_attr into a single line in early_stdout_state mod
- Split long variable assignment across lines in bin macro for better readability

This improves code consistency and readability without changing functionality.

Add a check to ensure stdout is writable before printing environment variables, preventing errors when stdout is closed. This uses a non-zero sentinel to trigger the check and mark write attempt.