feat(orchestrator): slice 5 — build the consolidated sidecar bundle image (#352)

Answers "where do we build the consolidated sidecar": nowhere, until now.

  * sidecar.py — `Sidecar.ensure_built()` (default no-op) + `DockerSidecar`
    now defaults its image to the real bundle (`bot-bottle-sidecars`) and
    `ensure_built()` builds it from `Dockerfile.sidecars` when
    `docker image inspect` shows it's missing (no-op when present or when no
    dockerfile is configured, e.g. a pre-pulled image). `image_exists()`
    added.
  * service.py — `ensure_sidecar()` now builds then runs.
  * __main__.py — `--sidecar` runs the consolidated bundle (build-if-missing).

Scope note: this builds + launches the bundle *container*; making the
running instance functional across bottles needs the per-bottle,
source-IP-keyed multi-tenant config + registration/reload, and routing
agent bottles to it — the next slices (added to PRD 0070's roadmap).

Tests: unit (docker mocked) — image_exists, ensure_built builds when
missing / no-op when present / no-op without a dockerfile / raises on build
failure; ensure_sidecar builds-then-runs; integration (gated, no heavy
build) — image_exists reflects real docker state. Full suite green (only
pre-existing /bin/sleep errors).

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

bot_bottle/orchestrator/service.py

@@ -83,9 +83,10 @@ class Orchestrator:
     # --- consolidated sidecar ----------------------------------------------
 
     def ensure_sidecar(self) -> None:
-        """Bring the single per-host sidecar up (idempotent). No-op when no
-        sidecar is configured."""
+        """Ensure the single per-host sidecar is built and up (idempotent).
+        No-op when no sidecar is configured."""
         if self._sidecar is not None:
+            self._sidecar.ensure_built()
             self._sidecar.ensure_running()
 
     def sidecar_status(self) -> dict[str, object]: