feat(reflect): R-reflect Phase-2a coproduct variant-enumeration + Path-3 conformance

src/v2/05_emit_rust.dag

@@ -1258,7 +1258,7 @@ fn emit_lib_rs_from_files(all_module_files: List<TextFile>, has_compiler_tests:
   // rest_transport_facts.rs and INVARIANTS bounded substrate seed).
   // These are not generated — they survive regen as non-generated files.
   let hand_maintained_mods = if has_compiler_tests {
-    "\npub mod v2_interpreter;\npub mod cli_run;\npub mod rest_transport_facts;"
+    "\npub mod v2_interpreter;\npub mod cli_run;\npub mod rest_transport_facts;\npub mod coproduct_reflection;"
   } else {
     ""
   }

src/v2/stage0/src/bin/regen_stage0.rs

@@ -97,6 +97,7 @@ const GENERATED_STAGE0_FILES: &[&str] = &[
 
 const HAND_MAINTAINED_STAGE0_FILES: &[&str] = &[
     "cli_run.rs",
+    "coproduct_reflection.rs",
     "rest_transport_facts.rs",
     "v2_compiler_dag_collect.rs",
     "v2_interpreter.rs",