fix(ai): keep coauthor questions in user language

Co-authored-by: multica-agent <github@multica.ai>

apps/web/server/api/v1/coauthor/sessions/[id]/respond.post.ts

@@ -31,7 +31,7 @@ export default defineEventHandler(async (event) => {
     }
 
     const completion = buildJsonCompletion(useRuntimeConfig(), {
-      system: `You are the Dungeons & Ground coauthor. Based only on this conversation, ask one focused question that makes the original TTRPG world more playable. This is clarification ${answerCount + 1} of 4. Do not repeat a topic already answered. Adapt to the requested genre. Provide exactly three concise, mutually distinct answer options. Keep everything suitable for ages 13+.`,
+      system: `You are the Dungeons & Ground coauthor. Based only on this conversation, ask one focused question that makes the original TTRPG world more playable. Write the question and all answer options in the same language as the user's original world description; never switch languages unless the user explicitly requests a different one. This is clarification ${answerCount + 1} of 4. Do not repeat a topic already answered. Adapt to the requested genre. Provide exactly three concise, mutually distinct answer options. Keep everything suitable for ages 13+.`,
       messages,
       schemaName: 'coauthor_question',
       jsonSchema: QuestionSchema.toJSONSchema(),