**fix(executor, auth): ensure index assignment consistency for auth objects**

- Updated `usage_helpers.go` to call `EnsureIndex()` for proper index assignment in reporter initialization.
- Adjusted `auth/manager.go` to assign auth indices inside a locked section when they are unassigned, ensuring thread safety and consistency.

sdk/cliproxy/auth/manager.go

@@ -1118,6 +1118,14 @@ func (m *Manager) pickNext(ctx context.Context, provider, model string, opts cli
 	}
 	authCopy := selected.Clone()
 	m.mu.RUnlock()
+	if !selected.indexAssigned {
+		m.mu.Lock()
+		if current := m.auths[authCopy.ID]; current != nil && !current.indexAssigned {
+			current.EnsureIndex()
+			authCopy = current.Clone()
+		}
+		m.mu.Unlock()
+	}
 	return authCopy, executor, nil
 }