Function check_mikrotik_command 

pub const fn check_mikrotik_command(cmd: &str) -> &str

A minimal const validator that enforces some basic MikroTik command rules:

1. Must start with /.
2. No empty segments (no //).
3. Only allows [a-zA-Z0-9_-] plus space or slash as separators.
4. No consecutive spaces or slashes.

Panics at compile time if invalid.