**fix(auth): resolve index reassignment issue during auth management**

- Fixed improper handling of `indexAssigned` and `Index` during auth reassignment.
- Ensured `EnsureIndex` is invoked after validating existing auth entries.

sdk/cliproxy/auth/manager.go

@@ -207,8 +207,12 @@ func (m *Manager) Update(ctx context.Context, auth *Auth) (*Auth, error) {
 	if auth == nil || auth.ID == "" {
 		return nil, nil
 	}
-	auth.EnsureIndex()
 	m.mu.Lock()
+	if existing, ok := m.auths[auth.ID]; ok && existing != nil && !auth.indexAssigned && auth.Index == 0 {
+		auth.Index = existing.Index
+		auth.indexAssigned = existing.indexAssigned
+	}
+	auth.EnsureIndex()
 	m.auths[auth.ID] = auth.Clone()
 	m.mu.Unlock()
 	_ = m.persist(ctx, auth)