The terminal surface with no session used to be an empty frame, with the tab row's "+" the only
thing on it that did anything. It now holds a prompt, in the order ssh asks: "connect to:" takes a
saved host's name, matched exactly, with the hosts that match so far listed under it for Tab or a
click, or user@host[:port] for a machine that is not saved. A password line follows only when one
is needed, worded as ssh words it. Escape steps back a line; recent connections are listed below.
It is drawn by Avalonia in the WebView's rectangle, which the occlusion rule allows because the two
are exclusive: the prompt shows only while there are no tabs, the WebView only for a tab with a
session.
Saved hosts connect through a new VaultViewModel.ConnectToHostAsync, which the drawer's own connect
now goes through too, so every refusal is still made once. Each attempt now carries whether it may
act on the drawer's remember-password tick, and the prompt's may not: otherwise a tick left on in
a closed drawer would save a password typed at a prompt that never offered to keep anything.
Covered by nine ShellFlowTests cases and four ConnectPromptTests; manual check 7.10b.
