feat(orchestrator): MVP synthetic life-injection worker (SSH only)

Adds a new decnet orchestrate worker whose job is to keep the honeypot
ecosystem from looking suspiciously static — a frozen LAN with no
inter-host traffic and no filesystem aging is its own honeypot tell.

MVP scope:
- New OrchestratorEvent table + repo methods (purpose-built sibling
  to Log so synthetic events stay separable from attacker-driven ones).
- New orchestrator.{activity,file}.<decky_id> bus topics +
  system.orchestrator.health heartbeat.
- SSH-only driver. Traffic action runs python3 inside src container
  to TCP-connect dst:22 and read the SSH banner — real on-the-wire
  SSH-protocol traffic without shipping creds. File action drops or
  refreshes a small file via docker exec on the destination.
- Random scheduler (50/50 traffic/file when >=2 SSH-capable deckies
  are running). Diurnal shaping, role-aware pairing, and session-aware
  backoff are explicit non-goals for MVP.
- CLI registration, systemd unit (SupplementaryGroups=docker),
  worker-registry entry so the dashboard shows orchestrator health.
- 11 tests: scheduler policy, driver argv shape + injection-safety,
  end-to-end one-tick integration with FakeBus + SQLite.

tests/orchestrator/test_ssh_driver.py

@@ -0,0 +1,99 @@
+"""Driver tests with the docker subprocess mocked.
+
+We don't need a real Docker daemon to validate the driver's contract:
+it boils down to "build an argv, call _run, classify the result". A
+dependency-injected ``_run`` keeps the tests hermetic.
+"""
+from __future__ import annotations
+
+import pytest
+
+from decnet.orchestrator.drivers import ssh as ssh_driver
+from decnet.orchestrator.drivers.base import ActivityResult
+from decnet.orchestrator.scheduler import FileAction, TrafficAction
+
+
+@pytest.mark.asyncio
+async def test_traffic_success_classifies_on_ssh_banner(monkeypatch):
+    captured_argv: list[list[str]] = []
+
+    async def fake_run(argv):
+        captured_argv.append(argv)
+        return 0, "SSH-2.0-OpenSSH_9.6\r\n", ""
+
+    monkeypatch.setattr(ssh_driver, "_run", fake_run)
+    drv = ssh_driver.SSHDriver()
+    action = TrafficAction(
+        src_uuid="u1", src_name="decky-01",
+        dst_uuid="u2", dst_name="decky-02",
+        dst_ip="10.0.0.2",
+    )
+    result = await drv.run(action)
+    assert isinstance(result, ActivityResult)
+    assert result.success is True
+    assert result.payload["banner"].startswith("SSH-2.0-OpenSSH")
+    assert captured_argv[0][:3] == ["docker", "exec", "decky-01-ssh"]
+    assert captured_argv[0][-1] == "10.0.0.2"
+
+
+@pytest.mark.asyncio
+async def test_traffic_failure_when_banner_missing(monkeypatch):
+    async def fake_run(argv):
+        return 1, "", "Connection refused"
+
+    monkeypatch.setattr(ssh_driver, "_run", fake_run)
+    drv = ssh_driver.SSHDriver()
+    action = TrafficAction(
+        src_uuid="u1", src_name="decky-01",
+        dst_uuid="u2", dst_name="decky-02",
+        dst_ip="10.0.0.2",
+    )
+    result = await drv.run(action)
+    assert result.success is False
+    assert result.payload["rc"] == 1
+    assert "Connection refused" in result.payload["stderr"]
+
+
+@pytest.mark.asyncio
+async def test_file_action_invokes_docker_exec_on_dst(monkeypatch):
+    captured_argv: list[list[str]] = []
+
+    async def fake_run(argv):
+        captured_argv.append(argv)
+        return 0, "", ""
+
+    monkeypatch.setattr(ssh_driver, "_run", fake_run)
+    drv = ssh_driver.SSHDriver()
+    action = FileAction(
+        dst_uuid="u2", dst_name="decky-02",
+        path="/tmp/.cache-1700000000.tmp",
+        content="session=1700000000\n",
+    )
+    result = await drv.run(action)
+    assert result.success is True
+    assert result.payload["bytes"] == len("session=1700000000\n".encode())
+    argv = captured_argv[0]
+    assert argv[:3] == ["docker", "exec", "decky-02-ssh"]
+    assert argv[3] == "sh"
+    assert argv[4] == "-c"
+    # The shell payload must single-quote both the content and the path —
+    # any unquoted ``;`` or ``$`` here would mean a shell-injection bug.
+    sh_cmd = argv[5]
+    # Path appears (shlex.quote leaves safe paths unquoted) and content
+    # is single-quoted — that's the shell-injection-safe contract.
+    assert "/tmp/.cache-1700000000.tmp" in sh_cmd
+    assert "'session=1700000000\n'" in sh_cmd
+    assert "mkdir -p /tmp" in sh_cmd
+
+
+@pytest.mark.asyncio
+async def test_run_handles_missing_docker_binary(monkeypatch):
+    async def fake_create(*args, **kwargs):
+        raise FileNotFoundError("docker")
+
+    monkeypatch.setattr(
+        "asyncio.create_subprocess_exec", fake_create,
+    )
+    rc, out, err = await ssh_driver._run(["docker", "exec", "x", "true"])
+    assert rc == 127
+    assert "not found" in err