Right now you can open Claude Code in your project and prompt it "start a workflow that fans out subagents, each with a narrow scope, to look for {simplifications, correctness by construction opportunities, <insert your goal>} ranked by impact vs confidence, and then collate the findings into result.md". If you have the tokens, do more workflows that find more issues and/or vet and polish the findings already in the file.
I do that every time my weekly usage is about the reset to spend me last tokens.
Maintenance is becoming trivial, and anyone who thinks AI dooms you to an ever growing mudball apparently hasn't considered using AI for anything other than appending more code to the mudball.