fix(ui): improve dark-mode article highlight contrast

Tune TOC active highlight and code/mark highlight contrast in dark theme.

Author: Noveris-Teams

src/styles/global.css

@@ -131,6 +131,29 @@ a {
   padding-top: 2.6rem !important;
 }
 
+.astro-code .line {
+  display: block;
+  margin: 0 -0.55rem;
+  padding: 0 0.55rem;
+  border-left: 2px solid transparent;
+}
+
+.astro-code .line.highlighted,
+.astro-code .line[data-highlighted],
+.astro-code .line.diff.add,
+.astro-code .line.diff.remove {
+  background: hsl(214 100% 95% / 0.95) !important;
+  border-left-color: hsl(var(--accent) / 0.65);
+}
+
+[data-theme='dark'] .astro-code .line.highlighted,
+[data-theme='dark'] .astro-code .line[data-highlighted],
+[data-theme='dark'] .astro-code .line.diff.add,
+[data-theme='dark'] .astro-code .line.diff.remove {
+  background: hsl(214 100% 66% / 0.2) !important;
+  border-left-color: hsl(212 100% 73%);
+}
+
 [data-theme='light'] .astro-code,
 [data-theme='light'] .astro-code span {
   color: var(--shiki-light, #24292f) !important;
@@ -161,12 +184,17 @@ a {
 
 .toc-link.is-active {
   color: hsl(var(--accent-strong));
-  background: hsl(var(--accent) / 0.18);
+  background: hsl(var(--accent) / 0.2);
+  border-left: 2px solid hsl(var(--accent) / 0.72);
+  padding-left: calc(0.5rem - 2px);
   font-weight: 700;
 }
 
 [data-theme='dark'] .toc-link.is-active {
-  color: hsl(var(--accent));
+  color: hsl(210 100% 86%);
+  background: hsl(212 100% 60% / 0.3);
+  border-left-color: hsl(212 100% 73%);
+  box-shadow: inset 0 0 0 1px hsl(212 100% 68% / 0.35);
 }
 
 [data-toc-scroll] {
@@ -223,6 +251,20 @@ a {
   color: hsl(220 14% 74%);
 }
 
+.prose :where(mark) {
+  border-radius: 0.28rem;
+  border: 1px solid hsl(41 98% 54% / 0.42);
+  background: hsl(49 100% 75% / 0.5);
+  color: hsl(224 46% 20%);
+  padding: 0.04em 0.32em;
+}
+
+[data-theme='dark'] .prose :where(mark) {
+  border-color: hsl(44 100% 64% / 0.52);
+  background: hsl(44 100% 52% / 0.3);
+  color: hsl(48 100% 88%);
+}
+
 .link-underline {
   background-image: linear-gradient(hsl(var(--accent)), hsl(var(--accent)));
   background-position: 0 100%;