Function acronym_aware_snake_phrase 

pub fn acronym_aware_snake_phrase(variant_name: &str) -> String

Convert a PascalCase variant name into a human readable phrase that preserves canonical acronyms.

Examples:

• "IoError" → "IO error"
• "OcrError" → "OCR error"
• "PdfParse" → "PDF parse"
• "HttpRequestFailed" → "HTTP request failed"
• "Other" → "other"