Load the model's chat_template.jinja (or tokenizer_config.json
chat_template field) at startup and render it with minijinja instead of
hardcoded per-model prompt builders.
Custom Jinja functions: strftime_now (date formatting), raise_exception
(template validation errors). Falls back to Qwen3 ChatML template if
no Jinja template is found.
Removes the hardcoded build_prompt_gpt_oss() — the model's own template
now drives prompt formatting, matching llama.cpp's behavior exactly.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>