Path.suffix

Return the last file suffix (extension) including the leading dot.

Semantics are modeled after Python's pathlib:

• Returns the last suffix including the leading dot, e.g., "archive.tar.gz" → ".gz".
• Returns an empty string when there is no suffix.
• Dotfiles without any additional dots (e.g., ".bashrc") are considered to have

no suffix: this returns an empty string and the entire name is the stem.