wfzyx/von: decision files

Chat template, settings and head of wfzyx/von for pipeline("decision") (transformers#49566). The backbone stays the original checkpoint.

from transformers import pipeline

decide = pipeline("decision", model="wfzyx/von", decision_config="ArthurZ/von")
decide({"state": "I was charged twice and want a refund.", "questions": {"refund": {"type": "noul", "instructions": "Is a refund requested?"}}})

• decision_template.jinja: the chat template; <|mark|> marks the positions the head reads.
• decision_config.json: temperatures and option order.
• decision_head/: VonDecisionHead, converted from option_marker.pt of the original.
• decision_test.json: a request and the input ids that the original code builds for it, used by the tests.

Derived from wfzyx/von (Apache-2.0).