Every compose invocation used -p decnet so fleet + every topology
lived in one docker compose project. --remove-orphans, run during
fleet pre-up cleanup and on every topology teardown / rollback, then
swept every container in the project not listed in the current compose
file — wiping sibling topologies and the flat fleet along with the
intended target.
Parameterize project on _compose / _compose_with_retry / _compose_ps
(default FLEET_COMPOSE_PROJECT="decnet"). Add _topology_compose_project
that returns decnet-topo-<id8>, and pass it through every topology
compose call site (master deploy_topology + rollback + post-deploy ps,
master teardown_topology, agent apply, agent teardown, all four live
service mutations on topology deckies). Fleet calls keep the default
and are unaffected.
Migration: live containers from before this fix remain in the shared
"decnet" project and need a one-time manual cleanup before they're
reachable to the new topology code paths.
