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>

ui/dr-ui/ui/library.slint

@@ -4372,9 +4372,19 @@ export component LibraryGrid inherits Rectangle {
         // the count beside the buttons elides, so the row genuinely has a
         // smaller footprint than its natural one and a window with room for
         // the shrunk row should get it shrunk rather than scrolled.
+        //
+        // The row scrolls sideways once it outgrows the window, which at a
+        // desktop width it does. Export is pinned beside it rather than inside
+        // it: last in a scrolling row put it past the right edge, and with a
+        // mouse nothing says the row scrolls — so batch export looked like a
+        // feature the library did not have. A layout, not the Rectangle, is
+        // the parent of the two, or both sit at the origin and overlap.
+        HorizontalLayout {
+            padding-right: Theme.gap;
+            spacing: Theme.gap-sm;
+
         Flickable {
-            width: 100%;
+            horizontal-stretch: 1;
-            height: 100%;
             viewport-height: self.height;
             viewport-width: max(self.width, selection-row.min-width);
 
@@ -4605,6 +4615,9 @@ export component LibraryGrid inherits Rectangle {
                 clicked => { root.open-membership(); }
             }
 
+        }
+        }
+
         // TRACES: FR-EXP-7 | NFR-ARCH-3
         // Export the selection, and stop the batch that is running.
         //
@@ -4613,11 +4626,11 @@ export component LibraryGrid inherits Rectangle {
         // somewhere — shifting the row under the pointer at the exact
         // moment the user is reaching for it.
         //
-            // Last on the bar because it is the last thing done to a
+        // Pinned at the right end of the bar, outside the scrolling row
-            // selection, and because it is the one control here that outlives
+        // (see above), because it is the last thing done to a selection
-            // the selection: the bar itself stays up for a running batch (see
+        // and the one control here that outlives the selection: the bar
-            // the note on the bar) so this is always reachable while there is
+        // stays up for a running batch, so this is always reachable while
-            // something to cancel.
+        // there is something to cancel.
         //
         // The count is in the label rather than behind a confirmation,
         // exactly as the paste above puts it there: "Export 40" read
@@ -4641,7 +4654,6 @@ export component LibraryGrid inherits Rectangle {
         }
         }
     }
-    }
 
     // TRACES: FR-UI-2 | FR-UI-4
     // The gesture reference. Last of the sheets, and above them all, because it