Devices: fixes from review round 11

- A headset set up while a bare alias is in use doesn't take over by itself;
  a login change from ~/.ssh/config waits for running installs.
- Saving a headset writes only the login fields that changed, and only if the
  block still holds the old ones.
- SSH, SFTP, power and remote desktop open with the same headset and address
  as every other command, and refuse when there's no address.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

ui/frame_host.py

@@ -257,9 +257,9 @@ def open_steam_link():
     return "Steam Link isn't installed; opened its download page"
 
 
-def open_rdp(alias):
-    """Remote desktop to the Frame's xrdp (user steamos)."""
-    host = ssh_hostname(alias)
+def open_rdp(alias, host=None):
+    """Remote desktop to the Frame's xrdp (user steamos), at `host` or where the alias points."""
+    host = host or ssh_hostname(alias)
     if MAC:
         if subprocess.run(["open", "-a", "Windows App"], capture_output=True).returncode == 0:
             return "Opened Windows App"