fix: exclude emphasis color styling from citation reference links (et al.) (#366)

* fix: exclude emphasis color styling from citation reference links

The theme's emphasis styling (color + semi-bold weight) was being applied
to <em> tags inside citation reference links, causing 'et al.' text in
references like 'Barillas et al. [2009]' to display with the emphasis
color instead of inheriting the link color.

Add 'a.reference em' overrides in base, dark theme, and color scheme
styles to reset em tags inside reference links to inherit from their
parent link element.

* fix: update sphinxcontrib-bibtex upper bound to <3 (was <=2.5.0)

Author: mmcky

pyproject.toml

@@ -64,7 +64,7 @@ doc = [
     "sphinx-copybutton",
     "docutils>=0.20",
     "plotly",
-    "sphinxcontrib-bibtex>=2.2.0,<=2.5.0",
+    "sphinxcontrib-bibtex>=2.2.0,<3",
 ]
 test = [
     "myst_nb",

src/quantecon_book_theme/assets/styles/_base.scss

@@ -154,6 +154,14 @@ em {
   color: var(--qe-emphasis-color, colors.$emphasis);
 }
 
+// Reset emphasis styling inside citation reference links
+// Prevents "et al." in references from inheriting emphasis color
+a.reference em {
+  font-style: normal;
+  font-weight: inherit;
+  color: inherit;
+}
+
 // Strong/bold styling - semi-bold weight with color
 strong,
 b {

src/quantecon_book_theme/assets/styles/_color-schemes.scss

@@ -24,6 +24,12 @@ body.color-scheme-gruvbox {
     font-weight: 600;
   }
 
+  // Reset emphasis styling inside citation reference links (gruvbox)
+  a.reference em {
+    color: inherit;
+    font-weight: inherit;
+  }
+
   strong,
   b {
     color: var(--qe-strong-color, colors.$gruvbox-definition);
@@ -44,6 +50,11 @@ body.color-scheme-gruvbox {
       color: var(--qe-emphasis-color, colors.$gruvbox-emphasis-dark);
     }
 
+    // Reset emphasis styling inside citation reference links (gruvbox dark)
+    a.reference em {
+      color: inherit;
+    }
+
     strong,
     b {
       color: var(--qe-strong-color, colors.$gruvbox-definition-dark);

src/quantecon_book_theme/assets/styles/_dark-theme.scss

@@ -153,6 +153,11 @@ body.dark-theme {
     color: var(--qe-emphasis-color, colors.$emphasis-dark);
   }
 
+  // Reset emphasis styling inside citation reference links (dark mode)
+  a.reference em {
+    color: inherit;
+  }
+
   strong,
   b {
     color: var(--qe-strong-color, colors.$definition-dark);