fix(gameplay): use AI-generated world companions

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

apps/worker/src/ai.ts

@@ -89,7 +89,7 @@ async function structuredRequest<T>(name: string, schema: JsonSchema, messages:
 export async function generateWorld(messages: Array<{ role: 'user' | 'assistant'; content: string }>): Promise<WorldStarter> {
   assert13Plus(...messages.map(message => message.content))
   const world = await structuredRequest('world_starter', WorldStarterSchema.toJSONSchema(), [
-    { role: 'system', content: 'You are the Dungeons & Ground world coauthor. Create an original 13+ private TTRPG setting in any requested genre. Never use protected settings or characters. Return exactly three NPCs and two factions. Make the opening immediately playable.' },
+    { role: 'system', content: 'You are the Dungeons & Ground world coauthor. Create an original 13+ private TTRPG setting in any requested genre. Never use protected settings or characters. Return exactly three NPCs, two factions, and three distinct persistent AI companion heroes created specifically for this universe. Give each companion complete playable mechanics, useful genre-appropriate equipment, and a persona that produces interesting party choices without overriding the human player. Make the opening immediately playable.' },
     ...messages,
   ], value => WorldStarterSchema.parse(value))
   // Moderate the entire typed object, including entity summaries, secrets and