Looks like latest version of ExtJS doesn't come with a scoped version of the gray theme. How to use SASS and Compass to generate a scoped version?
The accepted answer is not answering the question.
To get a scoped version the gray theme:
install Compass
Then, on command line, move to the ExtJs Sass folder e.g. /extjs/resources/sass
duplicate the file ext-all-gray.scss
add the line $scope-reset-css: true;
at the top of the file.
Then run: compass compile ext-all-gray-scoped.scss
This will create a file ext-all-gray-scoped.css
in the CSS folder which you can now use.