Mike 2026-08-20, revising the 2026-07-31 iGPU-only call with the 2026-08-04
finding that this UHD 630 has no HEVC encode entrypoint. runtime: nvidia +
NVIDIA_VISIBLE_DEVICES/CAPABILITIES on the plex service; /dev/dri stays.
Also brings the compose current with the live opt-in watchtower config, and
50-plex.sh now sources WATCHTOWER_NOTIFICATION_URL (carries the publish
token) from stacks.env, soft-gates on nvidia-smi, and adds the NVENC line
to the walk-away checks.