Take a third off both of the terminal's bars, and centre the cross in a tab

The bar the last commit put above a shell opened at 52 and the accessory row
under it at 50, both inherited from the arrangement they replaced rather than
measured against the one they are in. Neither is carrying a title or a sentence
any more — the top one holds two icons and a row of pills, the bottom one a
line of keys — so a third comes off each: 35 and 33.

Every height inside them came down too. The pills go 44 to 30, the icon squares
34 rather than 44, the keys 38 to 30. A bar that shrank around contents that
did not would not have saved anything; it would have moved the clipping
somewhere harder to see.

Two of those numbers had arguments written against them and both arguments
change rather than disappear. The pill was 44 because it contains the one
control on this head that is destructive with neither confirmation nor undo,
and that is now carried by width — the cross keeps its full 44-pixel column,
and what it gave up is vertical slack in a row where nothing sits above or
below it to be hit by mistake. The keys were 38 for the same kind of reason,
and the 44 that mattered there was always the width: ten keys flexed across
360dp is 32 pixels each, which is what the horizontal minimum exists to refuse.
Both comments say what replaced the reasoning rather than quietly showing a
smaller number.

The close cross was not vertically centred, and it was not a rounding error.
`Button.row` sets `HorizontalContentAlignment` and says nothing about the other
axis, so the glyph sat against the top of its own column while the label beside
it was centred by the stack panel it lives in. On the control that ends a
session that reads as a misprint. Both alignments are now stated, on the button
and on the text.

The `+` loses the accent and becomes the same `Button.icon` as the arrow across
from it. The two are a matched pair at either end of one bar — one leaves this
surface, one adds to it — and an accented one ranked itself above the way out.
The accent fill belongs to the floating `+` on HOSTS, which is the only action
on its screen; this one is not.

Five pixels between the renderer and the keys, as a margin rather than a
border. The renderer is a native child view and nothing Avalonia draws can sit
on top of it, so a hairline there would have to be a row of its own — and a
terminal whose last line of output is flush against a row of grey keys reads as
one surface that has gone wrong rather than as two that are different things.

The four places that named the old bar height are corrected, including manual
check 11.5, which asserted a number that would now fail.

src/DodoSSH.Client.Android/Views/PhoneShell.axaml

@@ -29,7 +29,7 @@
 
     The arithmetic is why. Header 56, strip 46, bar 64, and the terminal's own two rows on top of that: at
     360dp the shell was framed by about a third of the display, all of it about somewhere the user was not.
-    What takes their place is one 52-pixel bar drawn by the surface itself, carrying back on the left and
+    What takes their place is one 35-pixel bar drawn by the surface itself, carrying back on the left and
     the sessions and a + across from it. See TerminalScreen.axaml.
   -->