make start-core (called by install.sh step 6) used $(DCF) which includes
docker-compose.services.yml — that file declares cell-network as external:true.
On a fresh machine the network doesn't exist yet, so compose up failed with
"network cell-network declared as external, but could not be found".
Fix: add the same network-create idempotency guard that start and update
already have. Also add 26 regression tests (test_install_process.py) that
verify install.sh structure and that all start-* targets using DCF create
the network before running compose up.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
