FiLM+SLOT implementation + SLOT24 baseline for comparison

SLOT (Scored-position Learnable Optimization at Test-time):
- Per-sample delta [bsz,1,dim] + logit_bias [bsz,1,vocab]
- 24 AdamW steps with cosine LR on frozen hidden states
- Architecture-agnostic — works on any model with _encode()

PR openai#1313 (SLOT-24) achieves 0.8637 BPB on 8×H100.
PR openai#1229 achieves 0.9300 BPB. Both use SLOT on SOTA architecture.
Running SLOT24 baseline on our 1×H100 for fair comparison.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: yuyeon