Function retry_hint_from_io_error 

pub fn retry_hint_from_io_error(error: &Error) -> RetryHint

Converts a std::io::Error into a conservative RetryHint.

This helper classifies known transient I/O conditions as retryable and treats request, permission, filesystem-capacity, and data-shape errors as non-retryable. std::io::ErrorKind is non-exhaustive, so future or unclassified kinds are considered non-retryable until reviewed explicitly.