COLUMBIA — The cinderblock walls inside this prison psychiatric unit brim with bright colors, painted butterflies and messages of hope left in elegant scroll.“Always believe in yourself,” one sign reads.“Get out! Stay out! Succeed!” trumpets another.“Difficult roads often lead to beautiful destinations,” says a third.The buoyant aphorisms at Kirkland Correctional Institution might easily be dismissed as a cheery veneer masking the reality of lives confined by steel doors and razor wire. But they are not-so-subtle evidence of a marked transformation over the past decade in how the S.C. Department of Corrections treats its mentally ill inmates.After a class-action lawsuit filed...