There are a lot of subjective, ambigous instructions that really won't affect what Claude writes. Remember it's not a human, it's not performing careful reasoning over each individual LOC.
Context rot is a thing (https://news.ycombinator.com/item?id=44564248 ).
As of today, you cannot squeeze a true rule system out of a single file given as context. Many of us have done this mistake at some point – believing that you can specify arbitrarily many rules and that they'll be honored.
If you really care about every such rule, you'd have to create sub-agents, one per rule, and make the agents a required part of a deterministic (non-AI orchestrated) pipeline. Then costs would explode of course.