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).

lib/ww/syntax/typ.ww

@@ -569,6 +569,13 @@ export fn typeeq(a: *tinfo, b: *tinfo) bool = {
 		return true;
 	};
 	if (k == tykind.TY_NAMED) { return false; };	// nominal: only same ptr
+	// Enums are nominal (harec: an enum IS its alias type): distinct
+	// decls are distinct types even with identical storage/members.
+	// Falling into the primitive tail made ANY two enums equal — the
+	// variant matcher picked the first enum variant of a union for a
+	// value of the OTHER enum (live cs!=ww, wrong tag at runtime).
+	// Same-decl chased ends hit the a == b fast path above.
+	if (k == tykind.TY_ENUM) { return false; };
 	if (k == tykind.TY_TAGGED) {
 		// Structural: variant lists match position-by-position, and
 		// the nullable `(*T|void)` fold is part of identity. Mirrors