w6c,ww: re-emit ... union-spread marker in .wwi producer (M4 E3, #95)

The N_TTAGGED serializer emitted each variant via wwi_type but never
re-emitted the `...` prefix for TK_ELLIPSIS spread variants, so an
exported `(...inner | str)` round-tripped through .wwi as `(inner | str)`.
The consumer's checker then could not flatten inner's members into the
alias and variadic-assignability rejected bare members — under separate
compilation this broke fmt/log/getopt. Re-emit `...` before the variant
type, both stages; the producer stays purely syntactic (flatten/dedup
remain the consumer's type-store job, per ref/hare/hare/unparse/type.ha:290-300).

Gate: test/wcc/989_wwispread_sep.c — table-driven (2-arm + 3-arm spreads)
x both stages, asserts the marker survives the .wwi, the consumer binds
bare members under --sep (exit 0), and cs==ww .wwi byte-identity.

selfhost/cmd/w6c/main.combined.ww

@@ -45855,6 +45855,10 @@ fn wwitype(fd: i32, t: *syntax.node) void = {
 		let e: *syntax.node = t.list;
 		for (e != nil) {
 			if (e != t.list) { wputs(fd, " | "); };
+			// #95: re-emit the spread marker purely syntactically;
+			// the consumer's type-store flattens
+			// (ref/hare/hare/unparse/type.ha:290-300).
+			if (e.op == syntax.tkind.TK_ELLIPSIS) { wputs(fd, "..."); };
 			wwitype(fd, e);
 			e = e.next;
 		};