Pin "Export N" to the right of the library's selection bar

It was the last of a dozen buttons in a row that scrolls sideways once
it outgrows the window, which at a desktop width it does. The button
sat past the right edge and nothing says the row scrolls to a mouse,
so batch export of a selection looked like a feature the library did
not have. The rest of the row still scrolls; Export, which is also the
cancel for a running batch, now sits beside it and is always visible.

docs/gestures.md

@@ -372,7 +372,7 @@ A folded burst draws its earliest frame, which is a fact about the clock and not
 
 Distinct from Done, which leaves the mode entirely. Clearing keeps it, so the next selection can start straight away.
 
-<sub>`ui/dr-ui/ui/library.slint:4454`</sub>
+<sub>`ui/dr-ui/ui/library.slint:4464`</sub>
 
 ### Select everything the grid is showing
 
@@ -381,7 +381,7 @@ Distinct from Done, which leaves the mode entirely. Clearing keeps it, so the ne
 
 A scoped grid of two hundred frames is two hundred taps otherwise, and "all of them, except those three" is a far more common shape than the taps it took to say it.
 
-<sub>`ui/dr-ui/ui/library.slint:4471`</sub>
+<sub>`ui/dr-ui/ui/library.slint:4481`</sub>
 
 ### Take photographs out of a collection
 
@@ -390,4 +390,4 @@ A scoped grid of two hundred frames is two hundred taps otherwise, and "all of t
 
 The badge on a cell says a photograph is filed in three collections and never which. This is the sheet that names them, and the only way out of one the grid is not currently scoped to.
 
-<sub>`ui/dr-ui/ui/library.slint:4594`</sub>
+<sub>`ui/dr-ui/ui/library.slint:4604`</sub>