What? By your definition object orientation is a "framework" because it "helps you structure code" and is "a set of conventions that are optionally enforced by code". That's not a framework, that's a paradigm!
If a framework doesn't do something implicitly it's just a large library. If it's a set of conventions not backed by baked-in logic, it's a style guide.
A framework must CALL YOU. It usually gives you a piece of code that loads itself and lets you customize what it does by passing your code/configs to it. Then you tell it to run with what you gave it. The parts of the framework that you call yourself are actually "plug-ins" or basically framework-specific libraries.
If the framework never calls your code and you only call into the framework, that's always just a library. I would argue that actually it's easier to conflate a very full-featured library with a microframework because both really kind of call your code (especially when it's in the form of closures or a DSL).
You would never accidentally call a framework a library, though, because it's obvious that it's handling things for you. It's running everything behind the scenes and you just kind of advise it to do the things you want.