Idea: mark the compilation errors inline in the code instead of in a section aside.

It would be nice to see the errors in the code section, marked in the code line that has the error instead of being in a section aside.

Start by reviewing how compilation errors are currently presented beside the code section in the notebook interface. Define the inline presentation and verify that each error appears on the corresponding code line instead of in a separate aside.

Written by the indexing model from the issue text.