TXT2MTXT: combine text into MText, with its settings dialog

TEXT and MTEXT objects are merged into one MTEXT (top-down or in
selection order, word-wrapped or one paragraph per object, with the
original pitch kept as line spacing) or each TEXT and MTEXT line becomes
an MTEXT of its own. The SEttings option opens the Combine Text settings
dialog; the settings persist as profile values and are exposed as the
TXT2MTXT* variables and the txt2mtxt_settings automation action.

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

src/app/command_driver/mod.rs

@@ -445,6 +445,7 @@ impl OpenCADStudio {
             } => {
                 self.finish_qselect_sample(*state, tab_id, handle);
             }
+            CmdResult::OpenTxt2MtxtSettings => self.open_txt2mtxt_settings(),
             CmdResult::OpenAutoConstrainSettings => {
                 self.handle_open_auto_constrain_settings();
             }