Feat: Add renderer for Zyphra/ZAYA1-8B

[nreHieW]

Support renderer for the new Zyphra/ZAYA1-8B model.

Should only be open when Prime-RL PR#2529 is opened and merged.

Notes:

• The template always emits an empty system prelude, even when the caller did not pass one.
• Multi-turn bridging must strip that synthetic BOS + empty system prelude from subsequent turns.
• Tool calls use Zyphra's XML-ish <zyphra_tool_call><function=...> format.
• Thinking can be optionally truncated from history.

Validation

uv run pytest tests -k 'ZAYA1 or Zyphra'