fix(web): 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. This is clarification ${answerCount + 1} of 4. Do not repeat a topic already answered. Adapt to the requested genre. Use the language of the first user message for the question and every answer option unless the user explicitly requests another language. Provide exactly three concise, mutually distinct answer options. Keep everything suitable for ages 13+.`,
       messages,
       schemaName: 'coauthor_question',
       jsonSchema: QuestionSchema.toJSONSchema(),