fix: allow lexical import shadowing

test/wcc/data/paramshadowmod/neg_mcase.ww

@@ -1,9 +1,8 @@
-// neg_mcase — `match (r) { case let shadowmod: i64 => ... }` where
-// the per-arm binder shadows the imported module. N_MCASE wires
-// check_module_shadow before scope_define on cs->str, so the rule
-// fires at the case line.
+// Legacy neg_mcase, now a positive match-arm case. The import supplies the
+// tagged value before the arm binder exists; inside that arm shadowmod is the
+// closer i64 binding. Builds and runs 42.
 
-package paramshadowmod;
+package main;
 
 import shadowmod;
 
@@ -14,8 +13,8 @@ fn parse(n: i64) (i64 | i32) = {
 	return n;
 };
 
-export fn main() i32 = {
-	let r: (i64 | i32) = parse(42i64);
+fn main() i32 = {
+	let r: (i64 | i32) = parse(shadowmod.say(): i64);
 	let out: i64 = 0i64;
 	match (r) {
 	case let shadowmod: i64 => out = shadowmod;