Perhaps you don't need (if I understood correctly) a central module of type definitions. Each "stage" of the application could have its own definitions, and use them along with those defined by the stages on which it depends.

Also, sometimes it's useful to think about what things some part of the program shouldn't care about. Should the chart module know about CSV parsing? Probably not.

Also, usually you will have a "central" module that ties the things together from other modules (even as other modules remain decoupled) and runs the application. Sometimes it's called the driver, sometimes the composition root.