fix(update): retain the detached updater log mirror

hermes_cli/main_dashboard.py

@@ -325,16 +325,14 @@ class _UpdateOutputStream:
 def _install_hangup_protection(gateway_mode: bool = False):
     """Protect ``cmd_update`` from SIGHUP (→ SIG_IGN, inherited by pip/git children) and broken pipes
     (stdio wrapped in ``_UpdateOutputStream``). SIGINT/SIGTERM are left alone — legitimate cancels.
-    No-op in gateway mode (already detached). Returns state for ``_finalize_update_output``."""
+    Gateway updates are already detached, but still need the log mirror for the
+    Desktop progress watchdog. Returns state for ``_finalize_update_output``."""
     state = {
         "prev_stdout": sys.stdout, "prev_stderr": sys.stderr, "log_file": None, "installed": False}
 
-    if gateway_mode:
-        return state
-
     import signal as _signal
 
-    if hasattr(_signal, "SIGHUP"):
+    if not gateway_mode and hasattr(_signal, "SIGHUP"):
         # Non-main thread: update still runs, just without hangup protection.
         with contextlib.suppress(ValueError, OSError):
             _signal.signal(_signal.SIGHUP, _signal.SIG_IGN)