Bound source argument files to lexer interface

We have an abstract class **`SoureFile`** that the lexer works with.

It is necessary to make a class that will inherit from this abstract class. This class should be a bridge to transfer the source code to the lexer from the command line.

Start by locating the abstract `SoureFile` class and the lexer entry point, then trace how command-line source files currently reach the compiler. Define the concrete bridge class and verify that command-line source code can be passed through the lexer without bypassing its interface.

Written by the indexing model from the issue text.