feat(orchestrator): slice 13c(vii) — stable shared gateway CA

The consolidated gateway TLS-intercepts every bottle, so all agents must
trust ONE CA. Rather than host-generate + mount a CA, let the gateway's own
mitmproxy generate its CA into a persistent named volume and extract the
cert for agents — no host openssl, keeps gateway.py lean.

- DockerGateway mounts GATEWAY_CA_VOLUME at /home/mitmproxy/.mitmproxy so the
  self-generated CA survives container recreation (it must not rotate, or
  already-launched agents would stop trusting the gateway).
- ca_cert_pem(): read the CA cert (PEM) out of the running gateway
  (docker exec cat mitmproxy-ca-cert.pem) — the agent installs this into its
  trust store to accept the gateway's bumped certs.

pyright 0 errors; pylint 9.83/10; unit suite green (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

bot_bottle/orchestrator/gateway.py

@@ -31,6 +31,14 @@ GATEWAY_LABEL = "bot-bottle-orch-gateway=1"
 # the source IP the gateway attributes by is the address on this network.
 GATEWAY_NETWORK = "bot-bottle-gateway"
 
+# mitmproxy's CA dir in the bundle. A persistent named volume here keeps the
+# gateway's self-generated CA STABLE across container recreation — every agent
+# installs this one CA to trust the shared gateway's TLS interception, so it
+# must not rotate when the gateway restarts.
+MITMPROXY_HOME = "/home/mitmproxy/.mitmproxy"
+GATEWAY_CA_VOLUME = "bot-bottle-gateway-mitmproxy"
+GATEWAY_CA_CERT = f"{MITMPROXY_HOME}/mitmproxy-ca-cert.pem"
+
 # The real sidecar-bundle image + its Dockerfile. Kept as a local constant
 # rather than imported from backend.docker.sidecar_bundle, which would drag
 # the whole backend layer into the lean orchestrator (see #359); unify when
@@ -143,11 +151,26 @@ class DockerGateway(Gateway):
             "--name", self.name,
             "--label", GATEWAY_LABEL,
             "--network", self.network,
+            # Persist the self-generated CA so it survives restarts (agents
+            # trust it) — see GATEWAY_CA_VOLUME.
+            "--volume", f"{GATEWAY_CA_VOLUME}:{MITMPROXY_HOME}",
             self.image_ref,
         ])
         if proc.returncode != 0:
             raise GatewayError(f"gateway failed to start: {proc.stderr.strip()}")
 
+    def ca_cert_pem(self) -> str:
+        """The gateway's CA certificate (PEM) that agents install to trust its
+        TLS interception. Read from the running container; raises if the
+        gateway hasn't generated it yet (it's created on first mitmproxy
+        start)."""
+        proc = run_docker(["docker", "exec", self.name, "cat", GATEWAY_CA_CERT])
+        if proc.returncode != 0 or not proc.stdout.strip():
+            raise GatewayError(
+                f"gateway CA cert not available: {proc.stderr.strip() or 'empty'}"
+            )
+        return proc.stdout
+
     def stop(self) -> None:
         proc = run_docker(["docker", "rm", "--force", self.name])
         if proc.returncode != 0 and "No such container" not in proc.stderr:
@@ -157,4 +180,5 @@ class DockerGateway(Gateway):
 __all__ = [
     "Gateway", "DockerGateway", "GatewayError",
     "GATEWAY_NAME", "GATEWAY_LABEL", "GATEWAY_IMAGE", "GATEWAY_NETWORK",
+    "GATEWAY_CA_VOLUME", "GATEWAY_CA_CERT",
 ]

tests/unit/test_orchestrator_gateway.py

@@ -6,11 +6,15 @@ import unittest
 from unittest.mock import Mock, patch
 
 from bot_bottle.orchestrator.gateway import (
+    GATEWAY_CA_CERT,
     GATEWAY_NAME,
     DockerGateway,
     GatewayError,
 )
 
+
+_CA_PEM = "-----BEGIN CERTIFICATE-----\nMII...\n-----END CERTIFICATE-----\n"
+
 _RUN_DOCKER = "bot_bottle.orchestrator.gateway.run_docker"
 
 
@@ -53,6 +57,8 @@ class TestDockerGateway(unittest.TestCase):
         self.assertIn("bot-bottle-sidecars:latest", runs[0])
         # Runs on the shared gateway network so agents can reach it by IP.
         self.assertEqual(self.sc.network, runs[0][runs[0].index("--network") + 1])
+        # Persists its CA on a named volume so agents keep trusting it.
+        self.assertTrue(any("mitmproxy" in a for a in runs[0]))
 
     def test_ensure_running_creates_network_when_missing(self) -> None:
         calls: list[list[str]] = []
@@ -68,6 +74,17 @@ class TestDockerGateway(unittest.TestCase):
         creates = [c for c in calls if c[:3] == ["docker", "network", "create"]]
         self.assertEqual([["docker", "network", "create", self.sc.network]], creates)
 
+    def test_ca_cert_pem_reads_from_container(self) -> None:
+        with patch(_RUN_DOCKER, return_value=_proc(stdout=_CA_PEM)) as m:
+            self.assertEqual(_CA_PEM, self.sc.ca_cert_pem())
+        argv = m.call_args.args[0]
+        self.assertEqual(["docker", "exec", self.sc.name, "cat", GATEWAY_CA_CERT], argv)
+
+    def test_ca_cert_pem_raises_when_absent(self) -> None:
+        with patch(_RUN_DOCKER, return_value=_proc(returncode=1, stderr="No such file")):
+            with self.assertRaises(GatewayError):
+                self.sc.ca_cert_pem()
+
     def test_ensure_running_reuses_existing_network(self) -> None:
         calls: list[list[str]] = []