fix(compose): make the Send button a square that reads as one item

An Expanding vertical size policy stretched the button to the full height of
the header form beside it, while the icon and the label kept their natural
sizes. The result was a tall rectangle with the icon anchored near the top,
the label near the bottom, and a gap between them: two marks rather than one
control.

Fixed size, derived from the icon so the square still fits its contents if
toolbar_icon_size changes, and aligned vertically centre against the headers
so the whole button is centred rather than its contents. The icon grows to
the configured size plus 8, since at this scale it is the button's subject
and the word underneath is the caption.

Nothing in the layout or the actions could see this, which is why the test
now asserts the vertical policy and that width equals height. Both fail
against the previous code.

0 files changed, 0 insertions, 0 deletions