Your deployed application does not need any code that is strictly client. Meaning if your server side code does not reference a Widget (which is not likely) than it can be excluded from the classes folder. Typically any code in the client subfolder is not needed.
[I am however amazed that under your client folder you have over 2000 files??? Not my place to say, but I would look at why there is class explosion. Sounds like a maintenance nightmare.]
As for how, what are you using to build the war? Maven, Ant, etc. What ever you are using look at their documentation on how to exclude folders from the compile phase of the build process.