fix: start apps not in this service cgroup

sims/modules/launcher/apps.py

@@ -45,13 +45,27 @@ class AppProvider:
         return Box(name="slot-box", orientation="h", spacing=10, children=children)
 
     def activate(self, item: DesktopApp) -> None:
-        # Detach from sims's session so apps survive sims shutdown.
+        # Launch in a transient systemd --user scope so the app gets its own
+        # cgroup instead of inheriting sims.service's. start_new_session alone
+        # only changes POSIX session/pgid; systemd tracks units by cgroup and
+        # would kill children with sims on stop (default KillMode=control-group).
         if item.command_line:
             argv = [
                 t for t in shlex.split(item.command_line) if not _FIELD_CODE_RE.match(t)
             ]
             if argv:
-                subprocess.Popen(argv, start_new_session=True)
+                subprocess.Popen(
+                    [
+                        "systemd-run",
+                        "--quiet",
+                        "--user",
+                        "--scope",
+                        "--collect",
+                        "--",
+                        *argv,
+                    ],
+                    start_new_session=True,
+                )
                 return
         item.launch()