Is there a lightweight independent reader for .quest files so I can package it without requiring the full installation of Quest?
... and no.
Currently, Quest games either need Quest installed on Windows or to be uploaded to and played from this site.
The next Quest (definitely not this year) will output games as websites (plain old HTML, JS, and CSS), but the current version (and all previous versions) of Quest is dependent on Windows (or a Windows server).
Sorry, but the game runner is pretty much Windows itself (or something).
If you're making a gamebook, you can use Squiffy (also available on this site). It outputs websites.