Function path_record 

pub fn path_record(folded_abs_path: &[u8]) -> u64

The low-48-bit synthetic record number for a folded-WTF-8 absolute path.

crate::index::Frn::record masks to 48 bits, so only these bits steer identity; the high 16 bits are left zero. Birthday-bound collisions are ~n²/2⁴⁹ (well under 0.1% at the scope-mode target of ≤a few hundred thousand entries); a collision merely shadows one path and self-heals on the next walk (ADR-0024).