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>

tests/unit/test_gateway_init.py

@@ -64,11 +64,11 @@ class TestEnvForDaemon(unittest.TestCase):
         self.assertNotIn("X", self._BASE)
 
 
-class TestOrchestratorEnvScoping(unittest.TestCase):
-    """The control-plane signing key stays with the orchestrator; the pre-minted
-    `gateway` JWT goes to the data-plane daemons (issue #469 review). Scoping
-    them per-process keeps a compromised data-plane daemon from reading the key
-    and minting a higher-privilege token, even in the combined infra container."""
+class TestSigningKeyScoping(unittest.TestCase):
+    """The gateway never holds the control-plane signing key — it's the
+    orchestrator's, which runs in a separate container/VM. Its daemons present
+    the pre-minted `gateway` JWT instead; the key is stripped from every daemon's
+    env as defense-in-depth (issue #469 review)."""
 
     _BASE = {
         "PATH": "/usr/bin",
@@ -76,11 +76,6 @@ class TestOrchestratorEnvScoping(unittest.TestCase):
         "BOT_BOTTLE_ORCHESTRATOR_AUTH_JWT": "gw-jwt",
     }
 
-    def test_orchestrator_gets_key_not_jwt(self):
-        env = _env_for_daemon("orchestrator", self._BASE)
-        self.assertEqual("sk-x", env["BOT_BOTTLE_ORCHESTRATOR_TOKEN"])
-        self.assertNotIn("BOT_BOTTLE_ORCHESTRATOR_AUTH_JWT", env)
-
     def test_data_plane_daemons_get_jwt_not_key(self):
         for name in ("egress", "git-gate", "git-http", "supervise"):
             env = _env_for_daemon(name, self._BASE)