Hi derek, in Sitefinity 4, the website project is by default a Web Application Project, meaning as you mentioned that you need to build with any changes to the code.
It is possible to convert your web application project to a web site project, which was the native mode for 3.x. I wrote some blog posts in the past on this, which are below.
I haven't tested this recently, but have used it successfully in the past to work in a web site instead of a project. for smaller projects it can be easier to work in. However for larger projects and teams, I think web applications are the recommended way to go.
Converting Sitefinity 4 Beta Web Application Projects to Web Site Projects
Followup: Converting Sitefinity 4 Web Application Projects to Web Site Projects
Hope this is helpful!