fix SigSelect Jasmine: return test API from IIFE; pend touch specs on desktop

window.SigSelect was being clobbered by the IIFE's undefined return value
(var SigSelect = (function(){...window.SigSelect={...}}()) overwrites window.SigSelect
with undefined). Fixed by using return {} like RoleSelect does.

TouchEvent is not defined in desktop Firefox, so the 5 touch-related specs now
call pending() when the API is absent rather than throwing a ReferenceError.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/apps/epic/static/apps/epic/sig-select.js

@@ -258,7 +258,7 @@ var SigSelect = (function () {
     }
 
     // ── Test API ──────────────────────────────────────────────────────────
-    window.SigSelect = {
+    return {
         _testInit: function () {
             _focusedCardEl = null;
             _reservedCardId = null;