Embedding model purge classification

Trap: purging after any model-load-looking failure seems self-healing, but network, authorization, permanent HTTP, or vendored-model failures create a purge→redownload→fail loop that hammers Hugging Face Hub. Fix: purge only proven-corrupt cached models under <cacheDir>/<modelId>; never purge read-only vendored models. Match transformers.js inference dumps only against the leading log string, not later formatted arguments, and keep network/model-corruption signatures distinct.