refactor(orchestrator): rename Sidecar -> Gateway for the consolidated data plane

Retire "sidecar" for the consolidated per-host path (PRD 0070 naming
decision): the orchestrator is the umbrella/control plane, and the
egress/git/supervise data-plane unit it runs is the "gateway".

- git mv sidecar.py -> gateway.py and the two integration + one unit test
  files; DockerSidecar->DockerGateway, Sidecar->Gateway,
  SidecarError->GatewayError, SIDECAR_*->GATEWAY_*, ensure_sidecar->
  ensure_gateway, sidecar_status->gateway_status, container name
  bot-bottle-orch-sidecar->bot-bottle-orch-gateway.
- Prose rename across broker/registry/egress/policy_resolver + PRD 0070.
- Preserved: the image name bot-bottle-sidecars, the
  BOT_BOTTLE_SIDECAR_IMAGE env var, Dockerfile.sidecars, and PRD 0069's
  own stage-name cross-references (that doc still uses "sidecar").

No behavior change. Full unit suite green (1679 tests; the 13
test_sidecar_init /bin/sleep errors are pre-existing NixOS-local noise).

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

tests/integration/test_orchestrator_docker_gateway.py

@@ -1,7 +1,7 @@
-"""Integration: the consolidated Docker sidecar is an idempotent singleton.
+"""Integration: the consolidated Docker gateway is an idempotent singleton.
 
 Gated on a reachable Docker daemon. Uses a unique name so it never
-collides with a real per-host sidecar or a leftover from another run.
+collides with a real per-host gateway or a leftover from another run.
 """
 
 from __future__ import annotations
@@ -10,17 +10,17 @@ import secrets
 import subprocess
 import unittest
 
-from bot_bottle.orchestrator.sidecar import DockerSidecar
+from bot_bottle.orchestrator.gateway import DockerGateway
 from tests._docker import skip_unless_docker
 
 IMAGE = "busybox"
 
 
 @skip_unless_docker()
-class TestDockerSidecarIntegration(unittest.TestCase):
+class TestDockerGatewayIntegration(unittest.TestCase):
     def setUp(self) -> None:
-        self.name = "bot-bottle-orch-sidecar-itest-" + secrets.token_hex(4)
-        self.sc = DockerSidecar(IMAGE, name=self.name)
+        self.name = "bot-bottle-orch-gateway-itest-" + secrets.token_hex(4)
+        self.sc = DockerGateway(IMAGE, name=self.name)
         self.addCleanup(self.sc.stop)
 
     def _count(self) -> int:

tests/integration/test_orchestrator_docker_gateway_build.py

@@ -1,4 +1,4 @@
-"""Integration: DockerSidecar.image_exists reflects real docker state.
+"""Integration: DockerGateway.image_exists reflects real docker state.
 
 Gated on a reachable Docker daemon. Deliberately does NOT build the full
 sidecar bundle (a heavy, slow image build) — it exercises the `image_exists`
@@ -11,14 +11,14 @@ from __future__ import annotations
 import subprocess
 import unittest
 
-from bot_bottle.orchestrator.sidecar import DockerSidecar
+from bot_bottle.orchestrator.gateway import DockerGateway
 from tests._docker import skip_unless_docker
 
 IMAGE = "busybox"
 
 
 @skip_unless_docker()
-class TestDockerSidecarImageExists(unittest.TestCase):
+class TestDockerGatewayImageExists(unittest.TestCase):
     def test_image_exists_true_for_present_false_for_absent(self) -> None:
         # Ensure the tiny image is present (build_if_missing is disabled here
         # so this never triggers a Dockerfile.sidecars build).
@@ -26,9 +26,9 @@ class TestDockerSidecarImageExists(unittest.TestCase):
             ["docker", "pull", IMAGE],
             stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL, check=False,
         )
-        self.assertTrue(DockerSidecar(IMAGE, dockerfile=None).image_exists())
+        self.assertTrue(DockerGateway(IMAGE, dockerfile=None).image_exists())
         self.assertFalse(
-            DockerSidecar("bot-bottle-nonexistent:doesnotexist", dockerfile=None).image_exists()
+            DockerGateway("bot-bottle-nonexistent:doesnotexist", dockerfile=None).image_exists()
         )