ww imports: require imports before declarations

test/sep/sepimport_test.ww

@@ -20,8 +20,9 @@ package sepimport_test;
 //
 // declns (#23/#30 modfn leg) — a distinct local `fn localaa` and the
 // file-scoped imported qualifier aa both resolve (exit 6 = localaa() +
-// aa.helper()); the _vbu layout flips declaration/import order and must stay
-// byte-identical on {aa.s,aa.wwi,__root.s}; __root.s carries both calls.
+// aa.helper()); the _vbu layout reorders the valid declarations after its
+// import and must stay byte-identical on {aa.s,aa.wwi,__root.s}; __root.s
+// carries both calls.
 //
 // slttypepref (#58/#50 c1) — scopelookuptype must prefer the current
 // module's SK_TYPE when a param shadows a type leaf two modules both