Terminal: ask what to connect to when Terminal is pressed with nothing open

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.

docs/manual-checks.md

@@ -1404,6 +1404,23 @@ MACHINE box, which takes the same path — `VaultViewModel.ConnectToEndpointAsyn
 the two is in how the palette hands the password over, not in the connection. The headless half of this is
 `QuickConnectTests`; what it cannot do is dial.
 
+### 7.10b Pressing Terminal with nothing open asks what to connect to
+
+Close every terminal tab, then press **Terminal** on the rail.
+
+**Pass:** the terminal's frame holds a prompt — `connect to:` with the caret already on it, so typing works
+without a click. Type part of a saved host's name: the matching hosts appear under the line, Tab completes to
+the first, and Enter connects to it — asking `user@host:port's password:` first only if that host has no key
+or saved password. Type `user@host` for a machine that is not saved instead: Enter asks for its password, and
+the second Enter opens a tab for it. Escape steps back from the password to the name. Afterwards HOSTS has
+nothing new on it, and no credential was saved — even with "remember" ticked in a host's drawer earlier.
+
+**Failure means:** a prompt that needs a click before it takes typing is the terminal's WebView still holding
+the native keyboard focus — see `NativeKeyboardFocus`, which `ConnectPrompt.TakeKeyboard` calls. Anything drawn
+*under* a blank rectangle is the occlusion rule broken: the prompt may only show while no tab exists. A new
+credential in KEYS after connecting is the prompt's attempt acting on the drawer's tick, which
+`ShellFlowTests.ThePrompt_NeverSavesAPassword_EvenWithTheDrawersTickLeftOn` exists to stop.
+
 ### 7.11 A host or a bucket made now can be picked on FILES now
 
 With the files screen's picker open on an empty or short list, go to HOSTS and add a host — or to KEYS and