DGNIMPORT: reference naming, cells, text placement, curves, references

Name clashes, DGNIMPORTMODE and prefixing as the reference names them;
V7 cell copies, unshared cells and mirrored placements as blocks;
justified text and text nodes placed at their justification points with
the reference's MTEXT contents; B-spline curves as splines and 3D arcs and
ellipses in their own planes; every V8 level as a layer; design models
only; reference attachments translated, ignored or attached as underlays.
The colour index palette comes from the codec fix it depends on.

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

src/app/commands/styleprops.rs

@@ -1223,6 +1223,7 @@ impl OpenCADStudio {
                     | "SELECTIONCYCLING"
                     | "UCSDETECT"
                     | "SURFACEASSOCIATIVITY"
+                    | "DGNIMPORTMODE"
                     | "UCSORTHO"
                     | "UCSVIEW"
                     | "LAYOUTCREATEVIEWPORT"
@@ -1622,6 +1623,41 @@ impl OpenCADStudio {
                         }
                         return Some(self.finish_dispatch(cmd));
                     }
+                    if name == "DGNIMPORTMODE" {
+                        // Where DGNIMPORT puts the model: 0 a new drawing, 1 the
+                        // current one keeping its definitions, 2 the current one
+                        // with prefixed names.
+                        use crate::modules::insert::dgn_import::{set_settings, settings};
+                        let mut s = settings();
+                        let current = s.mode;
+                        match value
+                            .as_deref()
+                            .map(|v| v.trim().parse::<u8>().ok().filter(|v| *v <= 2))
+                        {
+                            Some(Some(mode)) => {
+                                if current != mode {
+                                    s.mode = mode;
+                                    set_settings(s);
+                                    self.save_config();
+                                }
+                            }
+                            Some(None) => {
+                                self.command_line
+                                    .push_error("Requires an integer between 0 and 2.");
+                                self.command_line.push_output(&format!(
+                                    "Enter new value for DGNIMPORTMODE <{current}>:"
+                                ));
+                                self.pending_setvar = Some(name.clone());
+                            }
+                            None => {
+                                self.command_line.push_output(&format!(
+                                    "Enter new value for DGNIMPORTMODE <{current}>:"
+                                ));
+                                self.pending_setvar = Some(name.clone());
+                            }
+                        }
+                        return Some(self.finish_dispatch(cmd));
+                    }
                     if name == "SURFACEASSOCIATIVITY" {
                         use crate::scene::model::sweep_model;
                         let current = i16::from(sweep_model::surface_associativity());