fix(commands): ADDSELECTED keeps CLAYER, adopts dimension style (#239)

Two follow-ups to ADDSELECTED:

- It no longer permanently changes the current layer/colour/linetype/
  lineweight. The template's properties are captured as the drawing
  defaults only while the launched draw command runs; a snapshot taken in
  cmd_add_selected is restored the moment that command ends (central hook
  in apply_cmd_result) or is interrupted by another command.
- Dimensions are supported: add_selected_verb maps each DimensionType to
  its DIM* command, and the template's dimension style is adopted as the
  current DIMSTYLE (restored afterwards). commit_entity_handle now stamps
  every new dimension with the current DIMSTYLE — the DIM commands left the
  default "Standard" on the entity, so a normal dimension also picks up
  the active style now.

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

src/app/commands/mod.rs

@@ -66,6 +66,9 @@ impl OpenCADStudio {
         if self.tabs[i].active_cmd.is_some() {
             self.tabs[i].scene.clear_preview_wire();
             self.tabs[i].active_cmd = None;
+            // Interrupting an ADDSELECTED draw with another command reverts its
+            // template-property override too (#239).
+            self.restore_add_selected_defaults();
         }
         // Starting any command leaves interactive PAN mode (the PAN arm below
         // re-enables it).