- implement Mistral model in llm/models/mistral/mistral.py with GroupedQueryAttention, SwiGLU, RoPE, sliding window attention
- add __init__.py for module export
- add config files for mistral training and generation
- update universal experiment runner to support Mistral model
- add notebook for Mistral experiments
- add universal runner run_llm_experiment.py with JSON-config driven LLM training / generation
- add configs for gpt, gpt2, llama (training/generation)
- remove individual train/generate scripts for each model
- update README with simple how-to for experiments block
BREAKING CHANGE: all llm_only experiments now run only through run_llm_experiment.py; legacy scripts removed
