Carrier PCB for a removable 5S 18.5 V 4000 mAh LiPo-powered Raspberry Pi 400 workstation. Provides protected input, independent low-voltage cutoff, dedicated fused 5.1 V USB-C Pi output, 5 V USB-C LCD output, 12 V center-positive KVM output, cooling-fan power, and a safety-interlocked USB-C PD 5S charging path. This project remains under engineering review and is not fabrication-ready.