Better introduce each section

[Witiko]

Currently, most sections start with a sentence "In this section, we ...". However, it would be better to preface these sentences with a short description of the problem we are solving. For example: "In the future, an \acro{AI} agent might examine our code, identifying any regressions that our modifications have inadvertently caused. For the moment, regression testing demands a plethora of manually created files, which detail the behavior of our code and outline the methods for its validation. [\par?] In this section, we describe the on-disk files used in our framework: test files, formats, commands, and templates. We also show how we use them for testing".