chore: link renderer workarounds to slint issue

ui/components/on-screen-surface.slint

@@ -3,6 +3,7 @@
 // with its content paints its fill and border only from just above the window
 // to below the bottom of any screen, so cut edges, with their corner radius and
 // border, stay out of view. Its width must follow the window.
+// Go back to a plain Rectangle once a Slint release fixes slint-ui/slint#14250.
 export component OnScreenSurface {
     in property <brush> background;
     in property <length> border-radius;

ui/views/mail-reading-pane.slint

@@ -445,9 +445,9 @@ export component MailReadingPane inherits Rectangle {
     );
     private property <length> rendered-email-height: root.email-viewport-width * EmailReader.width-ratio * root.email-content-aspect + (root.remote-images-blocked ? 60px : 0px);
     // Slint's software renderer (CPU mode, Android) panics when it paints a
-    // rectangle reaching past ±32767 physical pixels (#35). Surfaces that grow
-    // with the message paint only this visible part of the scroll content; the
-    // margin keeps a cut edge, with its corner radius and border, out of view.
+    // rectangle past ±32767 physical pixels (#35). Surfaces that grow with the
+    // message paint only the visible scroll content, with a margin for cut edges.
+    // Remove this clamping once a Slint release fixes slint-ui/slint#14250.
     private property <length> paint-margin: 32px;
     private property <length> paint-left: -email-scroll.content-x - root.paint-margin;
     private property <length> paint-right: -email-scroll.content-x + email-scroll.visible-width + root.paint-margin;