feat: the table's four row/column inserts are big buttons

Rows & Columns follows Word: four big buttons carrying a 28px glyph and a
two-line label, with the three deletions folded into one Entfernen dropdown
beside them so the group keeps its width.

Two lines cost the band 12px (--w-ribbon-h 96 -> 108). The labels size to
min-content, not max-width, which a wrapped box ignores; and the inserts drop
the reserved caret slot, without which the group's foot label sits 8px below
every other group's.

src/styles/global.css

@@ -280,8 +280,9 @@
   --w-accent-soft: #e8f1fb;
   --w-menu-shadow: 0 8px 24px rgb(0 0 0 / 18%);
   --w-font: 'Segoe UI', -apple-system, BlinkMacSystemFont, Roboto, sans-serif;
-  /* Body height: three control rows plus the group-label row. A tuning knob. */
-  --w-ribbon-h: 96px;
+  /* Body height: three control rows plus the group-label row, and a big button's
+     label may take two of them. A tuning knob. */
+  --w-ribbon-h: 108px;
 }
 
 /* Word's dark mode: the Fluent dark neutrals, and the accent lightened because