cgen: peel *fn field types for local struct-field callees

fnptrcalleetfn's N_DOT arm accepted only a bare N_TFN field tnode, so
a call through a field declared `cb: *fn(...)` missed, fell through to
the name registry, and emitted CALL cb(SB) — an undefined symbol
(loud at link; cstage calls the stamped ptr-to-fn indirectly). Same
TPTR peel the N_IDENT arm already had. Fixture fnptrfield_call covers
the by-value and via-pointer shapes; corpus pin 1478/2956.

selfhost/cmd/wcc/cgenutil.ww

@@ -108,6 +108,18 @@ fn fnptrcalleetfn(c: *cgen, callee: *syntax.node) *syntax.node = {
 			let ft: *syntax.node = fi.tnode;
 			if (ft != nil) {
 				if (ft.kind == syntax.nkind.N_TFN) { return ft; };
+				// `cb: *fn(...)` — same TPTR peel as the N_IDENT
+				// arm above; without it the field-call fell through
+				// to the name registry and emitted CALL <leaf>(SB)
+				// (undefined symbol — loud at link, but cstage
+				// resolves the stamped ptr-to-fn and calls indirect).
+				if (ft.kind == syntax.nkind.N_TPTR) {
+					if (ft.lhs != nil) {
+						if (ft.lhs.kind == syntax.nkind.N_TFN) {
+							return ft.lhs;
+						};
+					};
+				};
 			};
 			return nil;
 		};