Move the library's routes and status onto its own Slint global

The scan/opening/status/error lines, offline mode and its retry, pinning a
collection offline, the sync and thumbnail-sweep state, and the callbacks
that route the grid to a rescan, a sync, another library, a panorama merge
or an export — the last of what AppWindow still carried under the
library- prefix — move onto the `Library` global started earlier on this
branch. Rust reaches them through window.global::<Library>() rather than
window.set_/get_/on_/invoke_ on the root.

library-visible is the one name that stays: it is computed from
active-page and active-view, the shell's own routing state, which a
global cannot read. AppWindow now declares no other library- property or
callback.

ui/dr-ui/src/collections_ui/trash.rs

@@ -12,7 +12,7 @@ use dr_catalog::Catalog;
 use dr_types::ImageId;
 use slint::ComponentHandle;
 
-use crate::{AppWindow, Collections};
+use crate::{AppWindow, Collections, Library};
 
 use super::controller::CollectionsController;
 use super::tree_sync::refresh_tree;
@@ -56,7 +56,9 @@ pub(super) fn start_trash(
     }
 
     log::info!("moving {} image(s) to the trash", moves.len());
-    window.set_library_status(format!("Moving {} to the trash…", moves.len()).into());
+    window
+        .global::<Library>()
+        .set_library_status(format!("Moving {} to the trash…", moves.len()).into());
     // The images are leaving the grid; a selection pointing at them would
     // survive as a set of ids the user can no longer see.
     ctl.clear_selection();
@@ -131,7 +133,9 @@ pub(super) fn start_restore(
     }
 
     log::info!("restoring {} image(s) from the trash", moves.len());
-    window.set_library_status(format!("Restoring {}…", moves.len()).into());
+    window
+        .global::<Library>()
+        .set_library_status(format!("Restoring {}…", moves.len()).into());
     // The images are leaving the trash view, so a selection pointing at them
     // would survive as ids the user can no longer see.
     ctl.clear_selection();
@@ -214,7 +218,7 @@ pub(super) fn drain_trash(
                         if failed > 0 {
                             job.detail(format!("{failed} failed"));
                         }
-                        w.set_library_status(status.into());
+                        w.global::<Library>().set_library_status(status.into());
                     }
                     TrashMessage::Done { moved, failed } => {
                         // Reported honestly, including the partial case: "38 of
@@ -233,7 +237,7 @@ pub(super) fn drain_trash(
                         } else {
                             job.fail(status.clone());
                         }
-                        w.set_library_status(status.into());
+                        w.global::<Library>().set_library_status(status.into());
                         if let Some(first) = failed.first() {
                             w.global::<Collections>()
                                 .set_collection_error(first.as_str().into());