In an era when last year's indie wunderkind is too often this year's studio sellout, screenwriter-director John Sayles stands apart, his rugged self-reliance a beacon to aspiring filmmakers wishing to make complex pictures that say something. His limited experience within the studio system (1983's "Baby, It's You" for Paramount; 1988's "Eight Men Out" at Orion) convinced him that easing the financial burden was not worth the resultant loss of artistic freedom; subsequently he has steered his own path, working in Hollywood only as script doctor or screenwriter for hire. Between assignments,