T10a feedback: toasts with undo and a hover-held clock, notifications and their center, alert, banner, callout, inline and status messages, empty state; root focus scopes take lost focus

src/theme/tokens.rs

@@ -189,7 +189,7 @@ impl Theme {
         px(16.0)
     }
 
-    /// Gap between a mini window and the screen edge.
+    /// Gap between the edge of a screen or window and what floats by it: a mini window, a toast stack.
     pub fn window_margin(&self) -> Pixels {
         px(24.0)
     }
@@ -243,6 +243,16 @@ impl Theme {
         px_to_rems(440.0)
     }
 
+    /// Width of a toast stack.
+    pub fn toast_width(&self) -> Rems {
+        px_to_rems(360.0)
+    }
+
+    /// Widest a centered block of prose runs, such as an empty state's help.
+    pub fn prose_width(&self) -> Rems {
+        px_to_rems(320.0)
+    }
+
     /// Narrowest a menu's panel gets.
     pub fn menu_width(&self) -> Rems {
         px_to_rems(200.0)