feat(field): table formula buttons, block placeholders, attribute fields on insert, plot-time field stamping

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/app/update/file.rs

@@ -3764,7 +3764,20 @@ impl OpenCADStudio {
         task
     }
 
+    /// A plot gives its fields (PlotDate) the plot time, as the reference
+    /// stores it; the hosts are redrawn before the plot reads the scene.
+    pub(in crate::app) fn stamp_plot_fields(&mut self) {
+        let i = self.active_tab;
+        let hosts = crate::entities::field::stamp_plot_fields(&mut self.tabs[i].scene.document);
+        if !hosts.is_empty() {
+            let changes: Vec<_> = hosts.into_iter().map(|h| (h, crate::scene::ChangeKind::Modified)).collect();
+            self.tabs[i].scene.bump_entities(&changes);
+            self.tabs[i].dirty = true;
+        }
+    }
+
     fn print_all_pages(&mut self) -> Result<Vec<crate::io::pdf_export::PdfPageInput>, String> {
+        self.stamp_plot_fields();
         let available = self.tabs[self.active_tab].scene.layout_names();
         let selected: Vec<String> = self
             .print_all_layouts
@@ -5337,6 +5350,9 @@ impl OpenCADStudio {
         }
         self.active_modal = None;
         self.reset_modal_geometry();
+        if !preview {
+            self.stamp_plot_fields();
+        }
 
         // Extents, Window and Display use one plot path in both spaces. Only
         // Paper-space Layout is special: it uses the physical sheet bounds.