Function read_config_toml 

pub fn read_config_toml() -> Result<(PathBuf, DocumentMut), MantaError>

Reads the manta CLI configuration file (cli.toml) and parses it as TOML, honoring MANTA_CLI_CONFIG.

Returns both the file path (for later writing via write_config_toml) and the parsed DocumentMut, which preserves comments and formatting for in-place edits.

Errors

• MantaError::IoError if the file cannot be read.
• MantaError::TomlEditError if the contents are not valid TOML.