Function parse 

pub fn parse(input: &[u8]) -> Result<XmlIndex<'_>>

Parse XML bytes and build a structural index.

This is the main entry point. Returns an XmlIndex that can be queried with XPath expressions.

Uses the fastest available parser for the input:

• NEON two-stage classifier for attribute-dense XML (>1 tag per 8 bytes)
• memchr-based scanner for text-heavy/mixed XML (sparse tags)

Both produce identical structural indices and pass 327/327 XPath conformance.