Function default_data_dir 

pub fn default_data_dir() -> Option<PathBuf>

Get the default data directory path for agent-diva files

Uses the system’s local data directory (e.g., %LOCALAPPDATA% on Windows, ~/Library/Application Support on macOS, ~/.local/share on Linux) and appends “agent-diva/files”.

Returns

• Some(PathBuf) - The default data directory path
• None - If the local data directory cannot be determined