refactor(orchestrator): split conflated sidecar image into orchestrator + gateway images

One image — `bot-bottle-sidecars:latest`, built from `Dockerfile.sidecars` —
served two unrelated roles: the egress/git-gate/supervise *data plane* and
the orchestrator *control plane* (which ran the same image with the entrypoint
overridden to `python3 -m bot_bottle.orchestrator`). The control plane is
stdlib-only, so it needed none of the mitmproxy/git/gitleaks payload it was
riding on — while being the most secret-dense process on the host (PRD 0070's
"secret concentration").

Split into two purpose-built images:

- `Dockerfile.gateway` -> `bot-bottle-gateway:latest` — the data plane
  (renamed from Dockerfile.sidecars; identical contents).
- `Dockerfile.orchestrator` -> `bot-bottle-orchestrator:latest` — a lean
  `python:3.12-slim` runtime; the bind-mounted `bot_bottle` package supplies
  the code (so the #381 source-hash recreate semantics are unchanged).

`OrchestratorService` now takes distinct `image` (control plane, default
`ORCHESTRATOR_IMAGE`) and `gateway_image` (data plane, default `GATEWAY_IMAGE`)
instead of feeding one `self.image` to both, and builds the lean image
(build-if-missing) before starting the container. The per-bottle bundle
constants in `backend/docker/sidecar_bundle.py` now alias the gateway
constants so a bundle and the shared gateway can never drift onto different
images. The `bot-bottle-sidecars` *image* name and `Dockerfile.sidecars` are
gone; the per-bottle *container* name prefix (`bot-bottle-sidecars-<slug>`) is
intentionally left for a separate change.

Verified end-to-end: both images build; the lean image runs the control plane;
`ensure_running` brings up the orchestrator on `bot-bottle-orchestrator:latest`
and the gateway on `bot-bottle-gateway:latest` (distinct images) and reports
healthy.

Closes #384.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WBMWTEtQdJ4W5UrWuLHCck

bot_bottle/backend/docker/sidecar_bundle.py

@@ -1,30 +1,33 @@
 """Sidecar bundle constants + helpers for the Docker backend
 (PRD 0024).
 
-The bundle image (built by Dockerfile.sidecars, PRD 0024 chunk 1)
-runs egress + git-gate + supervise as one container per bottle
-under a small Python init supervisor. As of chunk 5 the bundle
-is the only shape — the legacy four-sidecar topology and its
-`BOT_BOTTLE_SIDECAR_BUNDLE` feature flag are gone."""
+A per-bottle sidecar bundle runs egress + git-gate + supervise as one
+container under a small Python init supervisor. As of PRD 0024 chunk 5
+the bundle is the only shape — the legacy four-sidecar topology and its
+`BOT_BOTTLE_SIDECAR_BUNDLE` feature flag are gone.
+
+The bundle's image is the **same data plane** as the consolidated
+per-host gateway (PRD 0070), so it is one image with one name and one
+Dockerfile: `bot-bottle-gateway` / `Dockerfile.gateway` (#384). These
+constants alias the gateway's so a per-bottle bundle and the shared
+gateway can never drift onto different images."""
 
 from __future__ import annotations
 
-import os
+from ...orchestrator.gateway import GATEWAY_DOCKERFILE, GATEWAY_IMAGE
 
 
-# Bundle image. Defaults to a built-locally tag (built from the
-# repo's Dockerfile.sidecars via compose `build:`). Operators
-# pinning to a published digest can override via env.
-SIDECAR_BUNDLE_IMAGE = os.environ.get(
-    "BOT_BOTTLE_SIDECAR_IMAGE",
-    "bot-bottle-sidecars:latest",
-)
-
-SIDECAR_BUNDLE_DOCKERFILE = "Dockerfile.sidecars"
+# The per-bottle bundle image == the gateway data-plane image (aliased so
+# there is one source of truth; the `BOT_BOTTLE_GATEWAY_IMAGE` env override
+# on the gateway constant applies here too).
+SIDECAR_BUNDLE_IMAGE = GATEWAY_IMAGE
+SIDECAR_BUNDLE_DOCKERFILE = GATEWAY_DOCKERFILE
 
 
 def sidecar_bundle_container_name(slug: str) -> str:
     """`bot-bottle-sidecars-<slug>`. Same prefix scheme as the
     per-sidecar containers it replaces, so the dashboard's
-    discovery-by-prefix logic keeps working."""
+    discovery-by-prefix logic keeps working. (The per-bottle *container*
+    name keeps the historical `sidecars-` prefix; only the *image* was
+    renamed to `bot-bottle-gateway` in #384.)"""
     return f"bot-bottle-sidecars-{slug}"