fix(cmdeploy): docker: route test commands through container via CHATMAIL_DOCKER

Tests SSH into the host and run systemctl/journalctl/env directly,
which fails on Docker deployments where services run inside the
container. When CHATMAIL_DOCKER is set (to container name), Remote
and SSHExec now wrap commands in `docker exec`. Without CHATMAIL_DOCKER,
behavior is unchanged.

cmdeploy/src/cmdeploy/sshexec.py

@@ -50,6 +50,9 @@ class SSHExec:
     FuncError = FuncError
 
     def __init__(self, host, verbose=False, python="python3", timeout=60):
+        docker_container = os.environ.get("CHATMAIL_DOCKER")
+        if docker_container:
+            python = f"docker exec -i {docker_container} python3"
         self.gateway = execnet.makegateway(f"ssh=root@{host}//python={python}")
         self._remote_cmdloop_channel = bootstrap_remote(self.gateway, remote)
         self.timeout = timeout

cmdeploy/src/cmdeploy/tests/plugin.py

@@ -402,6 +402,9 @@ class Remote:
             case "@local": command = []
             case "localhost": command = []
             case _: command = ["ssh", f"root@{self.sshdomain}"]
+        docker_container = os.environ.get("CHATMAIL_DOCKER")
+        if docker_container:
+            command += ["docker", "exec", docker_container]
         [command.append(arg) for arg in getjournal.split()]
         self.popen = subprocess.Popen(
             command,