Have you tried referencing a local copy of ext-all-debug.js?
Perhaps Chutzpah/PhantomJS are failing to access the sencha CDN and therefore ExtJS is not being loaded.
P.S.: I'd suggest you to use Chutzpah specific reference:
/// <chutzpah_reference path="../../Scripts/jasmine.js" />
instead of
/// <reference path="../../Scripts/jasmine.js" />
To avoid possible conflicts with other libraries that also use the reference command. More details here.