Cloud Run gen2 doesn't provide eth0 with a unicast IP, causing k3s flannel
to crash on every container start. k3s was also wrong architecture for
Cloud Run (HPA inside a container, k3s overhead for one process).
Changes:
- entrypoint.sh: replace k3s server with a bash watchdog loop that starts
soul-demo directly and restarts it on crash (3s backoff)
- Dockerfile.stage: remove k3s binary, soul-demo-image.tar, k3s manifests
and their associated dirs/envvars; keep soul-demo binary only
- stage.yaml: remove 'Download k3s binary' step; rename and simplify
soul-demo build step to compile binary only (no OCI image/tar)
- dev.yaml: update soul-demo placeholder step (binary not tar)
- manifest.el: document HAVE_CURL requirement since manifest.el has no
c_flags/link_flags directive support
will.anderson