Very much this. LLMs are not producing code humans can maintain unless you take your time with them and still care about the quality of the output.

Maybe someone has the perfect claude.md that solves this problem but I have not seen it.

CLAUDE.md (or AGENTS.md) is not good place to put all code change rules, because these rules would dillute the context and "distract" the agent e.g. during bugs triage or business analysis.

Instead modularize the knowledge with skills and specialized MD files. Agent should lazy load what is needed to do focused work.

Skills have usage description metadata, but with free files you can simply instruct agent with CLAUDE.md to load them, e.g.: "Before you attempt to change any frontend code first load and follow `docs/{JS|HTML|CSS}_coding_rules.md`".