v3.49.15 — Mistral Large 4 at its list price; two more verified tool fallbacks

Mistral's launch promotion ended and blockrun moved mistral/mistral-large-4
from $0.68/$2.09 to $1.36/$4.18. The offline price table follows, so session
cost estimates match what the gateway bills.

@blockrun/router-core moves to 8773a99. A live probe confirmed well-formed
tool calls from deepseek/deepseek-v4.1-flash and openai/gpt-6.1-sol, so
auto routing can fall back to them on tool turns, behind the configured
chains. No primary changes on the core's decision snapshot.