The core consolidation win: one persistent sidecar per host, shared by
every bottle, instead of a sidecar bundle per bottle. Safe to share
because the attribution invariant (source IP + identity token) lets the
sidecar map each request to the right bottle.
* orchestrator/sidecar.py — a backend-neutral `Sidecar` lifecycle
contract (mirrors LaunchBroker) + a `DockerSidecar` impl. The defining
behaviour is idempotent singleton: `ensure_running` starts the instance
if absent and is a no-op if it's already up, so N launches never spawn
N sidecars; `stop` is idempotent.
* orchestrator/dockerutil.py — a shared `run_docker` helper; DockerBroker
now uses it too (DRY with slice 3).
* service.py — the Orchestrator holds an optional `Sidecar`, exposes
`ensure_sidecar()` + `sidecar_status()`.
* control_plane.py — `GET /sidecar` reports it; __main__ gains
`--sidecar-image` and ensures the single sidecar on startup.
Tests: unit (docker mocked) — is_running, ensure idempotent (no-op when up,
starts when absent), failure raises, stop idempotent; Orchestrator sidecar
wiring/status; control-plane /sidecar; integration (gated) — ensure is a
real idempotent singleton (one container after two ensures), stop removes.
Full suite green (only pre-existing /bin/sleep errors); integration
verified locally against real docker.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WBMWTEtQdJ4W5UrWuLHCck
