refactor: remove leftovers from the orchestrator/gateway consolidation

Sweep for vestiges of the old combined-plane model and the pre-split shared
rootfs. Two are load-bearing, the rest are stale docs/comments:

- Bug: macOS `enumerate_active` only excluded the gateway container from the
  agent list, so after the split the orchestrator container
  (`bot-bottle-mac-orchestrator`, also `bot-bottle-`-prefixed) was enumerated as
  a phantom agent. Exclude both infra containers; test covers it.
- Dead code: the gateway `bootstrap.py` still carried an `orchestrator` daemon
  spec + `_OPT_IN_DAEMONS` + a signing-key/JWT env branch, all for the old
  combined container where the gateway process could also run the control plane.
  No backend ever requests it now — removed; the key-stripping stays as
  defense-in-depth.

Stale-comment reframes: "the/single infra container" -> the orchestrator +
gateway pair (or the specific plane); "shared rootfs / bb_role init / one
published rootfs" -> the per-plane rootfs + `role_init`; the deleted
Dockerfile.infra references in Dockerfile.orchestrator/.gateway; and the macOS
"one infra container ... same address" docstring + its now-false
share-one-address test (the planes are distinct containers with distinct
addresses).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

bot_bottle/backend/macos_container/backend.py

@@ -101,10 +101,10 @@ class MacosContainerBottleBackend(
             yield bottle
 
     def ensure_orchestrator(self) -> str:
-        """Bring up the per-host infra container (control plane + gateway) and
+        """Bring up the per-host pair (orchestrator + gateway containers) and
         return its control-plane URL — the on-demand entry point operator tools
         (`supervise`) call when no control plane is running yet. Mirrors
-        firecracker's infra-VM bring-up."""
+        firecracker's infra bring-up."""
         from .infra import MacosInfraService
         return MacosInfraService().ensure_running().orchestrator_url