What happens if you change the @import css to something like this:
<link rel="stylesheet" href="[[++site_url]]assets/templates/ravenflight/css/ravenflight.css">
I'm also a little concerned that you say your template code isn't reflected in the code area for the manager. A static file should import into that field, if you change something in the file it should also change in the manager, and conversely, the same with the manager. Change something in the manager field, the static file should update. If this isn't occurring, something is wrong.
Try deleting everything in the code field for the template, then chose your static file again and save the template. Does it show up? Try copying the template code, and paste into the code field in the template. Does it stick?
If you continue to have issues, make a new template and try again. I've seen resources not work at times no matter what I do, and the only option was to make a new one, which typically works fine. It stands to reason that a template resource could also be gorked in some way.