SACRAMENTO, Calif. — California commissioned an exhaustive study of whether its prisons are providing sufficient mental health care, an effort officials said they could use to try to end a 34-year-old federal lawsuit over how the state treats inmates with mental illness. But corrections officials won’t disclose basic details of the now-stalled study — even the cost to taxpayers for two consulting firms and more than two dozen national experts retained to examine the issue in 2023. State lawyers cited attorney-client privilege and ongoing litigation in denying KFF Health News’ public records re…