feat(tablestyle): editable General section (margins, flow-suppress toggles)

The Table Style editor's General fields are now editable: H/V cell margins
(buffers + Apply) and title/header row-suppressed toggles, loaded from the
selected style on select. Per-cell (Data/Header/Title) text/fill/border
editing remains a follow-up.

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

src/app/view.rs

@@ -117,6 +117,8 @@ impl OpenCADStudio {
                 styles,
                 &self.tablestyle_selected,
                 selected_style,
+                &self.ts_hmargin,
+                &self.ts_vmargin,
             );
         }
         if Some(window_id) == self.mlstyle_window {