Function format_dir 

pub async fn format_dir(path: &Path, mode: FmtMode) -> Result<(), EuvError>

Formats all Rust source files in the given directory that contain euv macros.

Recursively walks the directory tree, finds .rs files, and formats any euv macro invocations found within them.

Arguments

• &Path - The root directory to search.
• FmtMode - Whether to check or write formatting.

Returns

• Result<(), EuvError> - Indicates success or failure.