wcc: Hare-style enum [storage] { ... } type

`type Foo = enum [intT] { NAME [= expr], ... };`. Storage defaults
to i32; members auto-increment from 0 (or last+1) when `= expr` is
omitted, and value expressions can reference earlier siblings —
enough surface for io::mode-style flag enums (`RDWR = READ | WRITE`).

`Foo.MEMBER` folds to an N_INTLIT in the checker, typed as the
named enum. Binops on enum values yield the same enum (type_eq on
the named pointer), so `mode.R | mode.W` is a `mode`. Enum ↔ int
is a reinterpret-only `as` cast — same register, no tag wrap — so
`mode.RDWR as i32` and `1 as mode` both work without runtime ops.

`is`/`?`/`!` are still tagged-union-only. CSP runtime (chan/proc)
is unchanged; only the type-system slot is touched here.

cmd/wcc/ww.h

@@ -178,6 +178,7 @@ typedef enum {
 	TK_IS,		/* Hare-style type test: e is T */
 	TK_VOID,	/* `void` — both a type name and a zero-size value */
 	TK_YIELD,	/* `yield expr;` — value-return from a match arm */
+	TK_ENUM,	/* Hare-style `enum [storage] { ... }` type form */
 
 	TK_LAST		/* sentinel for tables */
 } Tkind;
@@ -300,6 +301,11 @@ typedef enum {
 	N_TBANG,	/* `!T` — error-flagged type. lhs = inner type. */
 	N_YIELD,	/* `yield expr;` — set the enclosing match's value-
 			 * return and jump to its end label. lhs = value. */
+	N_TENUM,	/* `enum [storage] { ... }` type form.
+			 * lhs = storage type expr or NULL (default i32);
+			 * list = chain of N_TENUMMEMBER. */
+	N_TENUMMEMBER,	/* enum member. str=name, lhs=value expr or NULL
+			 * (auto-increment when omitted). */
 
 	N_LAST
 } Nkind;
@@ -377,7 +383,11 @@ typedef enum {
 	TY_UNTYPED_STR,
 	TY_UNTYPED_RUNE,
 	TY_UNTYPED_BOOL,
-	TY_UNTYPED_NIL
+	TY_UNTYPED_NIL,
+	/* Appended at the tail to keep existing TY_* values stable —
+	 * lib/ww/typ.ww mirrors them as explicit `def` numbers. */
+	TY_ENUM		/* `enum [storage] { ... }`. sub=storage,
+			 * fields=member list (Tfield.offset = u64 value). */
 } TypeKind;
 
 typedef struct Tfield Tfield;