config.ssh_domains is only registered into wezterm's mux domain list
at process startup; ReloadConfiguration picks up simple value changes
(font, colors, etc.) but does not re-register newly added ssh domains.
Selecting a freshly-saved domain from the main menu before a full
restart fails with "domain name ... is invalid" since it's absent
from the mux's domain list. Updated the save notification to tell the
user a restart (not just reload) is required.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>