SimHash / 64-bit content fingerprint / near-duplicate detection / dedup hashing / locality-sensitive hash. Pure-local 64-bit SimHash over token-level k-shingles (default k=3) using FNV-1a. Two SimHashes are 'close' (small Hamming distance) iff the underlying texts share many shingles. Returns hex + decimal forms plus token + shingle counts. Useful for content dedup pipelines, plagiarism detection, and bot-content clustering.