derive-validate-blocks-retracted-rediscovery

Summary

The derive engine has a built-in guard against rediscovering ideas that were already rejected. When proposing new beliefs, it checks whether any proposal's ID is too similar to a retracted belief by comparing hyphen/colon-separated tokens, and blocks it if half or more of those tokens match. This means once a conclusion is retracted, the system won't keep re-deriving slight variations of it, but it also means legitimately new beliefs with coincidentally similar naming could get incorrectly blocked.