feat(macos): consolidated per-host gateway for the Apple backend (PRD 0070)

Re-enables the macos-container backend on the shared per-host orchestrator +
gateway, replacing the per-bottle companion container removed in #385. This is
the last backend in PRD 0070's roadmap.

Apple Container 1.0.0 forced three departures from the docker shape, each
verified against the live CLI (findings recorded in the networking spike):

- No `--ip`. The address is DHCP-assigned and knowable only once the container
  runs, so the order inverts: gateway up -> run agent -> read its address ->
  register. The identity token is minted by registration and therefore cannot
  be in the agent's run-time env; it rides the proxy URL applied at
  `container exec` time (bare `--env` names keep it off argv).
- No container DNS. The gateway can only be handed the control plane's IP, so
  the orchestrator starts first and the gateway is pointed at its address.
- No `network connect`. Networks are fixed at run time, so the shared host-only
  network is created up front; per-bottle networks would restart the gateway
  on every launch and defeat the consolidation.

The agent runs with `--cap-drop CAP_NET_RAW`: Apple grants NET_RAW by default,
which would let an agent forge a neighbour's source address on the shared
segment. NET_ADMIN is already absent, so this closes the source-address half of
PRD 0070's attribution invariant.

Verified end-to-end on real Apple Container 1.0.0: both images build, the
control plane comes up healthy, the gateway reaches it by IP, and a registered
agent gets 200 for a host in its routes and 403 for one outside them. Bring-up
is idempotent — a second launch does not churn the singletons.

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

tests/unit/test_orchestrator_lifecycle.py

@@ -14,7 +14,7 @@ from bot_bottle.orchestrator.lifecycle import (
     ORCHESTRATOR_SOURCE_HASH_LABEL,
     OrchestratorService,
     OrchestratorStartError,
-    _source_hash,
+    source_hash,
 )
 from tests.unit import use_bottle_root
 
@@ -57,7 +57,7 @@ class TestOrchestratorService(unittest.TestCase):
         # A healthy control plane already running the *current* bind-mounted
         # source is left alone — recreating it on every launch would drop
         # every other active bottle's in-memory egress tokens (#381).
-        current = _source_hash(self.svc._repo_root)
+        current = source_hash(self.svc._repo_root)
         calls: list[list[str]] = []
 
         def fake(argv: list[str]) -> Mock:
@@ -98,7 +98,7 @@ class TestOrchestratorService(unittest.TestCase):
         self.assertEqual(1, len(runs))
         self.assertIn(ORCHESTRATOR_NAME, runs[0])
         # the fresh container is labeled with the current hash, not the stale one
-        current = _source_hash(self.svc._repo_root)
+        current = source_hash(self.svc._repo_root)
         self.assertIn(f"{ORCHESTRATOR_SOURCE_HASH_LABEL}={current}", runs[0])
 
     def test_ensure_running_starts_orchestrator_container_when_absent(self) -> None: