This is basically how claude code works today. You have it /init a description of the project structure into CLAUDE.md that is used for each invocation. There is some implicit knowledge in the project about common frameworks and languages. Then when working on something between the explicit and implicit knowledge and the task at hand it will grep for relevant material in the project, load either full or parts of files, and THEN it will start working on the task. But it dynamically builds the context of the codebase based on searching for the relevant bit. Short-circuiting this by having a good project summary makes it more efficient - but you don't need to literally copy in all the code files.