Isolate Rust source facts

tests/redgate_test.sh

@@ -15,6 +15,7 @@ cargo test -p hemx-build generated_contract_fingerprint_is_deterministic --lib #
 cargo test -p hemx-build emits_generated_resources_from_heml --lib # spec: assurance/001 check
 cargo test -p hemx-build unkeyed_generated_target_diagnostic_is_structured --lib # spec: assurance/001 check
 test -f hemx-build/src/authoring.rs && grep -q '^mod authoring;$' hemx-build/src/lib.rs && ! grep -Eq '^fn (reject_selector_target_attrs|reject_unknown_hemx_attrs|known_hemx_attr|reject_invalid_hemx_attr_values|reject_invalid_hemx_attr_placement|reject_unkeyed_loop)\(' hemx-build/src/lib.rs # spec: architecture/001 check
+test -f hemx-build/src/rust_source.rs && grep -q '^mod rust_source;$' hemx-build/src/lib.rs && ! grep -Eq '^fn (context_type_for_heml_path|nearest_dir_with|rust_struct_facts_in|collect_rust_struct_facts|compact_tokens|loop_locals_for_surface|h_for_local_and_self_field|vec_element_type)\(' hemx-build/src/lib.rs # spec: architecture/002 check
 cargo test -p hemx-build no_op_build_preserves_generated_artifact_timestamps --lib # spec: build/003 check # spec: resource/005 check
 cargo test -p hemx-build changed_template_refreshes_generated_artifacts --lib # spec: resource/005 check
 cargo test -p hemx-derive --test surface surface_macro_preserves_inline_module_with_generated_file -- --exact # spec: derive/001 check