fix(layout): fully remove a deleted layout's record and references

delete_layout removed the Layout object and its entities but left the paper
space block record, the ACAD_LAYOUT dictionary entry and any standalone
PlotSettings behind. AutoCAD pairs every paper-space block record with a layout,
so the deleted tab could reappear on reopen. Also drop the block record, the
dictionary entry and the page setup so the layout is gone for good.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/scene/mod.rs

@@ -3889,6 +3889,38 @@ impl Scene {
         // Remove the Layout object itself.
         self.document.objects.remove(&layout_handle);
 
+        // Drop the layout's entry from the ACAD_LAYOUT dictionary so it does not
+        // dangle (and so AutoCAD doesn't try to recover a now-missing layout).
+        let dict_handle = self.document.header.acad_layout_dict_handle;
+        if let Some(ObjectType::Dictionary(d)) = self.document.objects.get_mut(&dict_handle) {
+            d.entries.retain(|(k, _)| k != name);
+        }
+
+        // Remove the now-empty paper-space block record.
+        let block_name = self
+            .document
+            .block_records
+            .iter()
+            .find(|b| b.handle == block_handle)
+            .map(|b| b.name.clone());
+        if let Some(bn) = block_name {
+            self.document.block_records.remove(&bn);
+        }
+
+        // Drop any standalone PlotSettings page setup tied to this layout.
+        let ps_handles: Vec<Handle> = self
+            .document
+            .objects
+            .iter()
+            .filter_map(|(h, o)| match o {
+                ObjectType::PlotSettings(ps) if ps.page_name == name => Some(*h),
+                _ => None,
+            })
+            .collect();
+        for h in ps_handles {
+            self.document.objects.remove(&h);
+        }
+
         // If the deleted layout was active, fall back to Model space.
         if self.current_layout == name {
             self.current_layout = "Model".to_string();