Split import_ui::wire into one function per section

The 188-line wire() registered the import page's callbacks in four
comment-delimited sections. Lift each into its own fn: wire_opening_and_closing,
wire_choosing_a_source, wire_options, wire_running. context stays generic
over C on each of the three functions that use it, matching how survey()
and start() already take it (impl Fn, implicitly Sized) rather than coercing
it to a trait object, which would have needed ?Sized added to those two
unrelated functions for no benefit.

ui/dr-ui/src/import_ui.rs

@@ -310,7 +310,17 @@ where
     let context = Rc::new(context);
     let on_imported = Rc::new(on_imported);
 
-    // --- opening and closing ---------------------------------------------
+    wire_opening_and_closing(window, &ctl, &context);
+    wire_choosing_a_source(window, &ctl, &context);
+    wire_options(window, &ctl);
+    wire_running(window, &ctl, &context, &on_imported);
+}
+
+/// Opening and closing.
+fn wire_opening_and_closing<C>(window: &AppWindow, ctl: &Rc<ImportController>, context: &Rc<C>)
+where
+    C: Fn() -> Option<Context> + 'static,
+{
     {
         let weak = window.as_weak();
         let ctl = ctl.clone();
@@ -351,8 +361,13 @@ where
             w.set_show_import(false);
         });
     }
+}
 
-    // --- choosing a source -------------------------------------------------
+/// Choosing a source.
+fn wire_choosing_a_source<C>(window: &AppWindow, ctl: &Rc<ImportController>, context: &Rc<C>)
+where
+    C: Fn() -> Option<Context> + 'static,
+{
     {
         let weak = window.as_weak();
         let ctl = ctl.clone();
@@ -395,8 +410,10 @@ where
             render(&w, &ctl);
         });
     }
+}
 
-    // --- options -----------------------------------------------------------
+/// Options.
+fn wire_options(window: &AppWindow, ctl: &Rc<ImportController>) {
     {
         let weak = window.as_weak();
         let ctl = ctl.clone();
@@ -465,8 +482,18 @@ where
             render(&w, &ctl);
         });
     }
+}
 
-    // --- running -----------------------------------------------------------
+/// Running.
+fn wire_running<C, F>(
+    window: &AppWindow,
+    ctl: &Rc<ImportController>,
+    context: &Rc<C>,
+    on_imported: &Rc<F>,
+) where
+    C: Fn() -> Option<Context> + 'static,
+    F: Fn() + 'static,
+{
     {
         let weak = window.as_weak();
         let ctl = ctl.clone();