refactor(macos): one infra container (control plane + gateway), fixes shared-DB races

Adopts the firecracker infra-VM pattern for macOS: the orchestrator control
plane and the gateway data plane now run in a SINGLE Apple container instead of
two. Apple Containers are lightweight VMs with separate kernels, so the prior
two-container design had both guests writing one bot-bottle.db over virtiofs,
where fcntl locks are not coherent across kernels — concurrent writes (the
orchestrator's registry vs the gateway supervise daemon's queue) could corrupt
it. One container = one kernel = coherent locking.

The DB moves onto a container-only Apple volume (bot-bottle-mac-db), never
bind-mounted from the host, so no host process opens the live file either. The
host CLI already reaches registry + supervise state over the control-plane HTTP
surface (cli/supervise.py uses OrchestratorClient), exactly as firecracker's
VM-only DB requires.

Two simplifications fall out of the single container:
- No DNS dance: the control plane and gateway daemons reach each other over
  127.0.0.1, so the orchestrator-before-gateway ordering (a workaround for
  Apple having no container DNS) is gone, along with the moved-IP recreate
  logic it needed.
- Net -243 lines.

Mechanics: the infra container runs from the gateway image with the
control-plane source bind-mounted read-only (like the docker orchestrator, so a
code change needs no rebuild) and a small sh -c init that starts both processes
(mirrors firecracker's _infra_init). Also implements the macOS backend's
ensure_orchestrator() and adds it to discover_orchestrator_url, so operator
tools (supervise) can bring up / find the control plane on demand — previously
the macOS backend died with "no orchestrator control plane".

Verified end-to-end on real Apple Container 1.0.0: the single infra container
comes up healthy (one address for control plane + gateway), both processes run,
the DB is written on the container-only volume, host-side supervise works over
HTTP, and a registered agent gets 200 for an allowed host / 403 for a denied
one. 1824 unit tests pass with `container` absent (CI parity), pyright clean,
pylint 9.89.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/unit/test_backend_selection.py

@@ -247,7 +247,7 @@ class TestHasBackend(unittest.TestCase):
 class TestEnsureOrchestrator(unittest.TestCase):
     """The backend-agnostic orchestrator bring-up entry point. Docker starts
     the orchestrator + gateway containers; firecracker boots the infra VM;
-    backends without one (macos-container) die with a pointer."""
+    macos-container starts the infra container."""
 
     def test_docker_delegates_to_orchestrator_service(self):
         b = get_bottle_backend("docker")
@@ -272,11 +272,16 @@ class TestEnsureOrchestrator(unittest.TestCase):
             url = b.ensure_orchestrator()
         self.assertEqual(url, "http://10.243.255.1:8099")
 
-    def test_macos_default_dies(self):
-        from bot_bottle.log import Die
+    def test_macos_delegates_to_infra_container(self):
         b = get_bottle_backend("macos-container")
-        with self.assertRaises(Die):
-            b.ensure_orchestrator()
+        with patch(
+            "bot_bottle.backend.macos_container.infra.MacosInfraService"
+        ) as service_cls:
+            service_cls.return_value.ensure_running.return_value.control_plane_url = (
+                "http://192.168.128.2:8099"
+            )
+            url = b.ensure_orchestrator()
+        self.assertEqual(url, "http://192.168.128.2:8099")
 
 
 if __name__ == "__main__":