feat(modify): TXTEXP turns text into its character outlines

TXTEXP replaces each selected TEXT and MTEXT with one polyline per
glyph contour, on the text's layer and with its properties: a
lightweight polyline for flat text, a 3D polyline for tilted text.
The outlines come from the same glyph tessellation the text renders
with, so stroke fonts give their strokes and outline fonts their
closed contours.

Refs D#1665

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

src/app/commands/dim.rs

@@ -1303,6 +1303,38 @@ impl OpenCADStudio {
                 }
             }
 
+            // TXTEXP — text becomes the polylines of its character outlines.
+            "TXTEXP" => {
+                let selected: Vec<_> = self.tabs[i]
+                    .scene
+                    .selected_entities()
+                    .into_iter()
+                    .filter(|(handle, _)| !self.tabs[i].scene.is_layer_locked(*handle))
+                    .collect();
+                if selected.is_empty() {
+                    use crate::modules::draw::select::SelectObjectsCommand;
+                    let cmd = SelectObjectsCommand::new("TXTEXP");
+                    self.command_line.push_info(&cmd.prompt());
+                    self.tabs[i].active_cmd = Some(Box::new(cmd));
+                } else {
+                    use crate::modules::draw::modify::explode::apply_explode_replacements;
+                    use crate::modules::draw::modify::txtexp::plan_text_explode;
+                    let replacements = plan_text_explode(&selected, &self.tabs[i].scene.document);
+                    let exploded = replacements.len();
+                    if exploded > 0 {
+                        self.push_undo_snapshot(i, "TXTEXP");
+                        apply_explode_replacements(&mut self.tabs[i].scene, replacements);
+                        self.tabs[i].dirty = true;
+                        self.refresh_properties();
+                        self.command_line
+                            .push_output(crate::tf!("{exploded} object(s) exploded.").as_ref());
+                    } else {
+                        self.command_line
+                            .push_info(crate::t!("TXTEXP: no text selected.").as_ref());
+                    }
+                }
+            }
+
             "OFFSET" => {
                 use crate::modules::draw::modify::offset::{is_offsettable, OffsetCommand};
                 let all_entities: Vec<_> = self.tabs[i]

src/app/control/mod.rs

@@ -277,6 +277,7 @@ fn command_category(name: &str) -> &'static str {
         "BREAK",
         "JOIN",
         "EXPLODE",
+        "TXTEXP",
         "STRETCH",
         "ARRAY",
         "PEDIT",
@@ -349,6 +350,7 @@ fn command_selection_policy(name: &str) -> &'static str {
         "CUTCLIP",
         "ERASE",
         "EXPLODE",
+        "TXTEXP",
         "GROUP",
         "LAYFRZ",
         "LAYLCK",