RAG Noisy Text: Spell-Check Limits

Classical spell-correction handles single typos but fails real RAG noise: user typos, transcription errors, and OCR mistakes. Levenshtein, BK-trees, Soundex, SymSpell, and n-gram Jaccard cover clean cases. Embeddings must absorb the rest, since valid-word typos like "coverage" versus "overage" escape detection.