Function compile_function_to_native_rust 

pub fn compile_function_to_native_rust(
    source: &str,
    target: &str,
) -> Result<Option<AotModule>, ParseError>

Generate the Rust SOURCE for an AOT-native cdylib of ONE function (HOTSWAP §Axis-3 / P14b): the target function plus its transitive callees (crate::codegen::function_slice), emitted through the normal ARCHITECT codegen, with the crate::codegen::codegen_native_tier_export shim appended so the loader can resolve the logos_native_<target> symbol. Mirrors compile_program_full’s front-end, then slices before codegen.

Returns Ok(None) when target is absent or outside the sound scalar ABI subset — the caller then keeps that function on VM+JIT (no AOT-native, no gap at the seam). Err only on a genuine parse/type error in the source.