Fix LangfusePromptGateway compile() to match langfuse SDK's Record<string,string> variable type

src/core/langfuse/LangfusePromptGateway.ts

@@ -19,7 +19,10 @@ export class LangfusePromptGateway implements PromptFetcher {
       version: prompt.version,
       config: (prompt.config ?? {}) as Record<string, unknown>,
       compile: (variables) =>
-        prompt.compile(variables) as { role: 'system' | 'user' | 'assistant'; content: string }[],
+        prompt.compile(variables as Record<string, string>) as {
+          role: 'system' | 'user' | 'assistant';
+          content: string;
+        }[],
     };
   }
 }