wcc: enums compare nominally; folded members keep their enum stamp

Two composing defects made a two-enum union mis-tag in wwstage
(live cs!=ww: `let e: (color|shape) = shape.BALL` stored tag 0 —
the color arm — while cstage stored 1). type_eq/typeeq had no
TY_ENUM arm, so ANY two enums fell into the primitive default and
compared equal; enums are nominal (harec: an enum IS its alias
type) and now compare by node identity only. Underneath, the
wwstage post-order revisit re-stamped the constant-folded enum
member (an N_INTLIT) as untyped_int, clobbering the enum stamp the
N_DOT fold applied, so the widen matcher fell to its first-variant
fallback -- the #59.9 N_BIN guard now twins on N_INTLIT (cstage
cexpr is single-pass and never clobbered).

internal/wwfixture/types.ww

@@ -1,13 +1,13 @@
 package wwfixture;
 
 def protocolversion: i32 = 1;
-def corpuscount: i32 = 1751;
+def corpuscount: i32 = 1752;
 def errorcount: i32 = 349;
 def compilecount: i32 = 21;
 def runcount: i32 = 209;
-def runexitcount: i32 = 1172;
-def nativecount: i32 = 3502;
-def corpushash: str = "0d0401f0d80ca682b0872343a62db4f91c0ff4c68e71f97cd5358cf92faffebc";
+def runexitcount: i32 = 1173;
+def nativecount: i32 = 3504;
+def corpushash: str = "d3c7b6a94918a9c9af14df029ef0cdf6d976a3f1351d41ff9db9a69b753cb016";
 
 type directive = enum i32 {
 	ERROR = 0,