feat: train transformer on HF A10G + heuristic improvements

fix: pin gradio>=4.44.1, modernize typing, clean ruff lint

feat: route plaintext→null_cipher; null_cipher 0→14 TP; acc=38.12%

feat: chi-based atbash/rot13/transposition detection; expand COMMON_WORDS

feat(data): add 20 sparse-label synthetic generators; dataset now 90 222 rows

feat: expand to 81 ciphers — improved heuristic, 12 new cipher generators, focal-loss training

Make Space HF-launch-ready: fix boot crash, add solver, expand eval, polish UX

ADA/mobile UI, pytest pythonpath, train_transformer PyArrow fix, enriched Explain Mode

10/10 polish: Compare Mode, Kasiski/Friedman, rich dataset schema, expanded tests/docs

Initial Cipher Detective AI public foundation