Brummel
84ba83dda3
First slice of the codegen module split. Pulls the run of free functions at the bottom of lib.rs into two purpose-named submodules, with no behaviour change: - synth.rs (216 lines): LLVM-IR shaping helpers — llvm_type, fn_sig_from_type, builtin_ail_type, builtin_effect_op_ret, type_descriptor, builtin_binop, c_byte_len, default_triple, ll_string_literal. - subst.rs (319 lines): monomorphisation pipeline — the derive_substitution + unify_for_subst + apply_subst_to_* family, plus qualify_local_types_codegen and descriptor_for_subst. lib.rs drops from 5295 → 4800 lines. Visibility is unchanged (submodules see lib.rs's private Result/CodegenError/FnSig through normal Rust scoping); call sites are unchanged in behaviour, only re-imported via 'use' at the lib.rs head. Motivation is the codebase-control conversation: lib.rs was the one navigability outlier flagged in the size sanity- check, and the 18g family closing left a clean window before the next iter. The remaining bulk (drop emission, match lowering, lambda lowering) will come out in follow-up commits, each an independent move-only refactor with full cargo test --workspace between.