Function session_name_from_path 

pub fn session_name_from_path(path: &Path) -> String

Generate a session name from a file path.

Rules:

• Uses the filename (not the full path)
• Strips leading dot (hidden files like .bash_history → bash_history)
• Replaces non-alphanumeric characters (except - and _) with -
• Collapses consecutive hyphens
• Trims leading/trailing hyphens
• Lowercases the result
• Falls back to imported-session if result is empty or invalid