Function validate_dataset 

pub fn validate_dataset(root: &Path) -> Result<ValidationResult>

Perform a full BIDS validation of a dataset directory.

Checks:

• dataset_description.json exists and has required fields
• README exists
• All files under sub-* directories follow BIDS naming conventions
• No unexpected files at the root level
• Metadata consistency (TR values match across runs, etc.)

This is a lighter-weight alternative to the official bids-validator; it catches the most common structural issues.

Errors

Returns an I/O error if the directory can’t be read.