merge: TEXTEDIT command + TEXTEDITMODE sysvar (#130)

Merge PR #130 (KarimJerbi) and resolve review findings:

- Conflict (settings.rs): keep current persisted-settings layout, append
  texteditmode field.
- Conflict (command/mod.rs): keep both new CmdResult variants — main's
  live-entity ops and the PR's text-edit suspend/resume.
- Bug: invalid TEXTEDITMODE value no longer aborts via the Measurement
  arm; it now re-prompts with the error and stays active.
- Dedup: single parse_texteditmode() helper replaces the value parsing
  duplicated across commands.rs, settings.rs and textedit.rs.
- Strip trailing whitespace.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/cmd_result.rs

@@ -1699,6 +1699,41 @@ impl OpenCADStudio {
                 self.ribbon.deactivate_tool();
                 return self.begin_text_edit(handle);
             }
+            CmdResult::SuspendForTextEdit { handle } => {
+                let is_editable = crate::app::text_inline::can_edit_text(handle, &self.tabs[i].scene.document);
+                if !is_editable {
+                    self.command_line.push_error("TEXTEDIT: selected entity is not text.");
+                    let prompt = self.tabs[i].active_cmd.as_ref().map(|c| c.prompt());
+                    if let Some(p) = prompt {
+                        self.command_line.push_info(&p);
+                    }
+                    return Task::none();
+                }
+                let cmd = self.tabs[i].active_cmd.take();
+                self.tabs[i].suspended_cmd = cmd;
+                self.tabs[i].snap_result = None;
+                self.tabs[i].scene.clear_preview_wire();
+                self.restore_pre_cmd_tangent();
+                self.ribbon.deactivate_tool();
+                return self.begin_text_edit(handle);
+            }
+            CmdResult::UndoDocument => {
+                let active = self.tabs[i].active_cmd.take();
+                self.undo_active_tab();
+                self.tabs[i].active_cmd = active;
+                let prompt = self.tabs[i].active_cmd.as_ref().map(|c| c.prompt());
+                if let Some(p) = prompt {
+                    self.command_line.push_info(&p);
+                }
+            }
+            CmdResult::SetTexteditMode(val) => {
+                self.texteditmode = val;
+                let display_val = if val { 1 } else { 0 };
+                self.command_line.push_output(&format!("TEXTEDITMODE set to {display_val}"));
+                self.tabs[i].active_cmd = None;
+                self.tabs[i].snap_result = None;
+                self.tabs[i].scene.clear_preview_wire();
+            }
             CmdResult::DdeditEntity { handle, new_text } => {
                 let mut updated = false;
                 if let Some(entity) = self.tabs[i].scene.document.get_entity_mut(handle) {