[Docs]: translate the #7395 OpenGateway and Mistral provider-guide sections #7405

Documentation problem type

Missing documentation

Documentation location

docs-site/src/content/docs/{ja,ru,zh-cn}/guides/providers.md (and other non-English locales)

What is wrong or missing?

#7395 adds two English provider-guide sections: the OpenGateway section on tool-result normalization and one-shot empty-completion recovery, and the Mistral section on cache keys and rate-limit recovery, including the reference row for retryOn429. Korean has the OpenGateway section. Japanese, Russian and Simplified Chinese have neither section, and the other locales lack the Mistral section. The translations do not contradict the English, but readers of those locales miss the new behavior. CodeRabbit flagged this on #7395 (review on d7e13ed).

What should the documentation explain instead?

Equivalent translations of both sections in each locale's guides/providers.md. For Mistral that means the default 6×10 s same-key retry, per-credential/model pacing, a Retry-After over budget stopping only same-key replays, and the opt-outs. For OpenGateway: string tool results, explicit 400 for unsupported parts, at most one empty-completion retry, and the exact-URL scope.

Suggested wording or example

Translate the English paragraphs added by #7395 in docs-site/src/content/docs/guides/providers.md.

Additional context or attachments

Kept out of #7395 to keep that PR's scope tight.

Checks

• I searched existing documentation issues.
• No secrets or personal information are included.