face_monochromatic_pairs: fix Remark 5.6 formatting

The disproof of Conjecture 5.5 used \[ ... \qquad\text{and}\qquad ... \]
to give both cycle definitions on a single display line. The second
half was too long to fit, producing a wide gap and an ugly line break.
Switch to align* with the two definitions stacked and aligned at =.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

papers/face_monochromatic_pairs/paper.tex

@@ -833,13 +833,12 @@ Figure~\ref{fig:no-two-constant-kempe-counterexample} exhibits a
 concrete counterexample: a cubic plane graph $H$ on $40$ vertices with
 a proper $3$-edge-colouring $\varphi$ (colours red/blue/green) in
 which both
-\[
+\begin{align*}
 K_{\mathrm{red},\mathrm{blue}}
-\;=\; \text{the outer $8$-cycle}
-\qquad\text{and}\qquad
+  &= \text{the outer $8$-cycle, and} \\
 K_{\mathrm{red},\mathrm{green}}
-\;=\; \text{the $12$-cycle (outer + upper-left ``ladder'' side)}
-\]
+  &= \text{the $12$-cycle (outer frame $+$ upper-left ``ladder'' side)}
+\end{align*}
 share the colour-red edge $(0, 7)$ and satisfy
 $h_\varphi \equiv -1$ on the vertex set of each. Globally $h_\varphi$
 takes value $+1$ on $16$ vertices and $-1$ on $24$ vertices, with all