docs: add transaction comment clarifying ObjectQL limitation per code review

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot

packages/plugins/plugin-auth/src/auth-manager.ts

@@ -109,6 +109,10 @@ export class AuthManager {
       return (_options: any) => ({
         id: 'objectql',
         ...adapter,
+        // ObjectQL does not yet expose a separate transaction context,
+        // so we pass the adapter itself.  better-auth patches this
+        // automatically when missing, but providing it avoids a
+        // runtime warning from getBaseAdapter().
         transaction: async <R>(cb: (trx: any) => Promise<R>): Promise<R> => cb(adapter),
       });
     }