M5: keep the pop-up raster rule in a helper after merging main (clippy cognitive complexity)

Main's signature-state redraw in apply_edit pushed the function over the
cognitive-complexity limit with the pop-up exception inline; the rule moves
into one_page_changed unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Pq7HyCHD1R3rywQBPCHXZA

crates/ui-egui/src/editing.rs

@@ -219,12 +219,7 @@ impl PdfCraftApp {
                         view.forms.unbaked.extend(unbaked);
                     }
                 } else if let Some(page) = one_page {
-                    // Comment and content edits change one page: keep every other raster. Opening,
-                    // closing or moving a pop-up changes none: the window is drawn over the page, and
-                    // a /Popup annotation paints nothing in the raster (ISO 32000-2 §12.5.6.14).
-                    if !matches!(edit, Edit::SetAnnotationPopup { .. }) {
-                        view.page_changed(page);
-                    }
+                    one_page_changed(view, &edit, page);
                 } else if let Some((changed_pages, unbaked)) = form_edit {
                     view.forms.unbaked.extend(unbaked);
                     for page in changed_pages {
@@ -946,6 +941,15 @@ fn content_page(edit: &Edit) -> Option<usize> {
     }
 }
 
+/// A comment or content edit changes one page, `page`: keep every other raster. Opening, closing
+/// or moving a pop-up changes none: the window is drawn over the page, and a /Popup annotation
+/// paints nothing in the raster (ISO 32000-2 §12.5.6.14).
+fn one_page_changed(view: &mut crate::DocView, edit: &Edit, page: usize) {
+    if !matches!(edit, Edit::SetAnnotationPopup { .. }) {
+        view.page_changed(page);
+    }
+}
+
 fn comment_page(edit: &Edit) -> Option<usize> {
     match edit {
         Edit::AddAnnotation(a) => Some(a.page),