docker compose --scale gives containers a hex hostname, not an ordinal

A container started by docker compose up --scale svc=N has its HOSTNAME set to the 12-hex container ID, not to the project-svc-3 name compose displays. Inside the container env yields only HOME/HOSTNAME/PATH/PWD/SHLVL -- there is no replica number, no service name, nothing to derive an identity from. The ordinal exists only host-side, as the label com.docker.compose.container-number. So any design where a scaled replica self-identifies (picking its own fixture set, config slice, or account) from its hostname is broken. Invert it: let the entrypoint be sleep infinity and have the host assign identity with docker compose exec --index=N, which addresses a specific replica and needs no docker socket inside the container. Also note a scaled service must publish no ports, or replica 2 fails on the port collision.