Add Herdr update and live handoff menu actions

The Ctrl+A h command menu gains two host-scoped actions: a plain
`herdr update` that streams updater output into the popup, and an
experimental update-and-hot-restart flow that verifies a live server
handoff and reconnects the originating Hub tab once the popup closes.

Remote updates use the remote host's own proxy settings. A standalone
helper reads literal proxy assignments from shell profiles and running
Clash/Mihomo listeners without executing startup files; Windows reads
process, user and machine proxy variables through PowerShell.

herdr_hub/cli.py

@@ -1452,7 +1452,17 @@ def command_control(arguments: argparse.Namespace) -> int:
     # Endpoint metadata is authoritative; popup environment may belong to another server.
     binary = resolve_herdr() if window.endpoint.kind == "local" else "herdr"
     control = HerdrControl(window.endpoint, binary, hub.ssh_bin)
-    return curses.wrapper(ControlMenu(control).run)
+    menu = ControlMenu(control)
+    result = curses.wrapper(menu.run)
+    if menu.reconnect_requested:
+        # Close curses first; respawning the client must not destroy its popup.
+        current = next((item for item in hub.managed_windows() if item.window_id == window.window_id), None)
+        if current is None or current.endpoint != window.endpoint:
+            raise HubError("服务器已更新，但原 Hub Tab 已改变；请手动连接目标 Session")
+        hub.reconnect(window.window_id)
+        hub.wait_for_window_startup(window.window_id)
+        hub.display_message("Herdr 服务器已更新，当前 Tab 已重新连接")
+    return result
 
 
 def command_keys(arguments: argparse.Namespace) -> int: