Part of the de-sidecar cleanup (#385 discussion): the per-bottle companion
container is the old architecture.
- Rename `bot_bottle/sidecar_init.py` → `gateway_init.py` (it's the gateway
image's PID-1 supervisor); env var `BOT_BOTTLE_SIDECAR_DAEMONS` →
`BOT_BOTTLE_GATEWAY_DAEMONS`; log prefix `sidecar-init:` → `gateway-init:`.
Update Dockerfile.gateway COPY/ENTRYPOINT and the test.
- Remove the dead per-bottle compose renderer from `backend/docker/compose.py`
(`bottle_plan_to_compose`, `_sidecar_bundle_service`, `_agent_service`, and
the network/bind/proxy helpers). Docker's live path uses
`consolidated_agent_compose`; only the compose *lifecycle* helpers
(up/down/ls/write) remain. Trim `test_compose.py` to the surviving helpers.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WBMWTEtQdJ4W5UrWuLHCck
