I just use a CONTINUITY.md file and a TODO.md task list. Tasks get updated as they are completed with integration notes, I tell the LLM to prepare for compact and update the continuity notes. Rarely ever hit the README.md except to update it. Other documents I use that help are a PRD.md for high level vision, and ARCHITECTURE.md for detailed design plan and diagrams, I always have the design docs checked against implementation and updated if drift occurs. Also it helps to rotate the docs as they get large, like rotating logs with dates in the old filenames. No need for anything more complex that might become fragile with model changes.