POaaS: Minimal-Edit Prompt Optimization as a Service to Lift Accuracy and Cut Hallucinations on On-Device sLLMs. - Jungwoo Shim; Dae Won Kim; Sun Wook Kim; Soo Young Kim; Myungcheol Lee; Jae-Geun Cha; Hyun-Hwa Choi (CoRR, 2026)