refactor(de-sidecar): remove the per-bottle companion-container architecture

The per-agent companion container (the egress/git-gate/supervise data
plane run once per bottle) is the pre-consolidation architecture. Remove
it and disable the backends that still depend on it, per the #385 thread.

- Delete `backend/docker/sidecar_bundle.py`; docker's live path uses the
  consolidated shared gateway, not a per-bottle bundle.
- Disable the firecracker and macos-container backends: their `launch()`
  fails closed (they launched a per-bottle companion; firecracker's
  consolidated relaunch is #354, macos follows). Their `enumerate` return
  empty and `cleanup` drop the companion-container discovery (firecracker
  keeps VMM/run-dir cleanup).
- Fail-close both backends' `egress_apply` reload (it signalled the
  per-bottle container); consolidated egress policy resolves per-request
  against the orchestrator, so gateway-side apply is a follow-up.
- Rename `egress_sidecar_env_entries` → `egress_gateway_env_entries`,
  `SIDECAR_PORTS` → `GATEWAY_PORTS`.
- Move the shared DockerBottlePlan fixture to `tests/unit/_docker_bottle_plan.py`;
  delete tests for the removed launch paths; update cleanup/egress-apply tests.

Docker consolidated launch verified end-to-end (multitenant isolation
integration test passes). macos/firecracker are intentionally disabled.

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

bot_bottle/backend/firecracker/enumerate.py

@@ -1,43 +1,14 @@
 """Active-agent enumeration for the Firecracker backend.
 
-The agent runs in a VM (no container to list), so a live bottle is
-identified by its running sidecar container `bot-bottle-sidecars-<slug>`
-— the same discovery-by-prefix the other backends use.
+The backend is disabled during the de-sidecar cleanup (#385) — it can't
+launch bottles, so there are none to enumerate. Real enumeration returns
+with the backend's consolidated relaunch (#354).
 """
 
 from __future__ import annotations
 
-import subprocess
-
-from ...bottle_state import read_metadata
 from .. import ActiveAgent
 
-_SIDECAR_PREFIX = "bot-bottle-sidecars-"
-
 
 def enumerate_active() -> list[ActiveAgent]:
-    result = subprocess.run(
-        ["docker", "ps", "--format", "{{.Names}}",
-         "--filter", f"name={_SIDECAR_PREFIX}"],
-        capture_output=True, text=True, check=False,
-    )
-    if result.returncode != 0:
-        return []
-    out: list[ActiveAgent] = []
-    for name in sorted(n.strip() for n in result.stdout.splitlines() if n.strip()):
-        slug = name[len(_SIDECAR_PREFIX):]
-        metadata = read_metadata(slug)
-        if metadata is None or metadata.backend != "firecracker":
-            # Skip sidecars owned by another backend (docker shares the
-            # container-name prefix).
-            continue
-        out.append(ActiveAgent(
-            backend_name="firecracker",
-            slug=slug,
-            agent_name=metadata.agent_name,
-            started_at=metadata.started_at,
-            services=(),
-            label=metadata.label,
-            color=metadata.color,
-        ))
-    return out
+    return []