fix: \sdcol emits English labels illegal/legal in [en] mode

Previously \sdcol hardcoded Chinese labels 非法/合法 regardless of the
package option. [en] mode now produces 'illegal' and 'legal'.

assets/superderive.sty

@@ -256,9 +256,9 @@
   \node[anchor=west, inner sep=0pt] (#1) at (\the\sd@cx,\the\sd@cy) {%
     \begin{tikzpicture}[baseline=(sd@mid)]
       \node[sd term, fill=sdCoral!30] (sd@B) {$\displaystyle #2$};
-      \node[font=\scriptsize, text=sdCoral, above=1pt of sd@B] {非法};
+      \node[font=\scriptsize, text=sdCoral, above=1pt of sd@B] {\sd@lblillegal};
       \node[sd term, fill=sdTeal!30, right=8mm of sd@B] (sd@G) {$\displaystyle #3$};
-      \node[font=\scriptsize, text=sdTeal, above=1pt of sd@G] {合法};
+      \node[font=\scriptsize, text=sdTeal, above=1pt of sd@G] {\sd@lbllegal};
       \coordinate (sd@mid) at ($(sd@B.east)!0.5!(sd@G.west)$);
     \end{tikzpicture}};%
   \pgfextractx{\sd@tmpx}{\pgfpointanchor{#1}{east}}%
@@ -267,8 +267,10 @@
 
 \ifder@en
   \def\sd@lblidea{Idea}\def\sd@lblrw{Rewrite}\def\sd@lblcaveat{Caveat}
+  \def\sd@lblillegal{illegal}\def\sd@lbllegal{legal}
 \else
   \def\sd@lblidea{思路}\def\sd@lblrw{改写}\def\sd@lblcaveat{注意}
+  \def\sd@lblillegal{非法}\def\sd@lbllegal{合法}
 \fi
 \newcommand{\sdsetlabels}[3]{\def\sd@lblidea{#1}\def\sd@lblrw{#2}\def\sd@lblcaveat{#3}}
 \newlength{\sd@raillen}