Function collect_flat_from_generated_rust 

pub fn collect_flat_from_generated_rust(
    root: &Path,
) -> Result<Vec<FlatInstruction>, CodegenError>

Collects normalized instruction variants from generated aarchmrs-instructions Rust source.

The root must point to an ISA folder such as .../aarchmrs-instructions/src/A64.

Errors

Returns CodegenError when filesystem traversal or source parsing fails.