fix(scaffold/paper): black hyperlinks, add mathtools, and unify bold vector style

mytoolkit/scaffolds/paper/main.tex

@@ -3,12 +3,15 @@
 \documentclass[review,3p,11pt]{elsarticle}
 
 \usepackage{amsmath,amssymb,amsfonts}
+\usepackage{mathtools}
 \usepackage{libertinus}   % portable serif + matching math (TeX Live bundled)
 \usepackage{graphicx}
 \usepackage{lineno}
 \usepackage{hyperref}
 % PDF outline expanded to two levels (section + subsection) by default.
-\hypersetup{bookmarksopen=true, bookmarksopenlevel=2}
+\hypersetup{colorlinks=true, allcolors=black, bookmarksopen=true, bookmarksopenlevel=2}
+
+\renewcommand{\vec}[1]{{\boldsymbol{#1}}}
 
 \journal{Journal Name}
 
@@ -43,7 +46,7 @@ Introduction section~\cite{example2024}.
 
 Methods section. An equation can be inserted as follows:
 \begin{equation}
-    \frac{\partial u}{\partial t} + \nabla \cdot \mathbf{F} = 0 .
+    \frac{\partial u}{\partial t} + \nabla \cdot \vec{F} = 0 .
 \end{equation}
 
 \section{Results and Discussion}