Add Lightroom's export and copy shortcuts to develop

Ctrl+E opens an export sheet: the export defaults on their own, over the
photograph, with an Export button. Ctrl+Shift+E exports straight away on
those defaults. There is no per-export copy of the settings, so what is
chosen in the sheet is saved as it is on the settings page, and the next
Ctrl+Shift+E uses it.

To make that one set of controls in two places, the export options move
out of the settings page into export.slint: an `ExportOptions` global
that Rust writes once, and two panels that read it. The window no longer
forwards forty `settings-*` properties to the page.

Ctrl+Shift+C opens a copy sheet with the edit-kind chips the preset
sheet already uses and a Copy button, which is how a paste leaves each
photograph's crop and rotation alone (Compose off). A and D step along
the roll beside the arrows. While either sheet is up the develop keys
stand down, so A cannot change the photograph behind the form, and
Escape closes it.

ui/dr-ui/src/gesture_book.rs

@@ -78,6 +78,27 @@ pub const GESTURES: &[Gesture] = &[
         pointer: "Press Paste in the top bar",
         keys: "Ctrl+V",
     },
+    Gesture {
+        title: "Choose which kinds of edit a copy carries",
+        section: "Develop",
+        touch: "Open Presets and toggle the kinds",
+        pointer: "Open Presets and toggle the kinds",
+        keys: "Ctrl+Shift+C, which offers Copy beside them",
+    },
+    Gesture {
+        title: "Export this photograph as the last one was",
+        section: "Develop",
+        touch: "Press Export in the top bar",
+        pointer: "Press Export in the top bar",
+        keys: "Ctrl+Shift+E",
+    },
+    Gesture {
+        title: "Choose how to export, then export",
+        section: "Develop",
+        touch: "Open Settings, then Export defaults",
+        pointer: "Open Settings, then Export defaults",
+        keys: "Ctrl+E",
+    },
     Gesture {
         title: "Change which group of adjustments is on screen",
         section: "Develop",
@@ -97,7 +118,7 @@ pub const GESTURES: &[Gesture] = &[
         section: "Develop",
         touch: "Tap a frame in the roll along the foot of the canvas",
         pointer: "Click a frame in the roll",
-        keys: "Right arrow or space for the next, left arrow for the one before",
+        keys: "Right arrow, D or space for the next; left arrow or A for the one before",
     },
     Gesture {
         title: "See the photograph before you edited it",