refactor: remove SLOT and TTT eval code (non-compliant / dead code)

SLOT (L-BFGS test-time adaptation) was ruled non-compliant in PR openai#675.
TTT was never enabled in any run and adds compliance risk. Removes:
- TTT and SLOT hyperparameter fields from Hyperparameters class
- eval_val_sliding_ttt() function (~155 lines)
- eval_val_slot() function (~175 lines)
- Both call sites in main()

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Omer Bese