Function write_file_reference_update_to_scratch 

pub unsafe fn write_file_reference_update_to_scratch(
    ptr: *mut u8,
    index: u32,
    path: &str,
) -> Result<(), String>

Write a file-reference update (index + new path) to scratch. Format: magic (u32), index (u32), length (u32), UTF-8 bytes.

Safety

ptr must point to a valid SHM allocation.