fix(website): use themed link colour for markdown links in dark mode

Raw markdown-injected <a> elements previously fell back to the browser's
default blue/purple link colours, which are harsh against the dark-mode
background. Route them through --brand-color-text-link-rest (and the
pressed/hover token) instead.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 80686fef-efe3-4cdd-8cd6-bfa61a5d0af6

website/src/components/brand/styles/dotnet-upgrade.module.css

@@ -538,6 +538,17 @@
   border-block-start: none;
 }
 
+/* Raw markdown links inherit the UA default blue/purple otherwise, which is
+   too harsh in dark mode; route them through the themed link token instead. */
+.articleSection a {
+  color: var(--brand-color-text-link-rest);
+}
+
+.articleSection a:hover,
+.articleSection a:focus-visible {
+  color: var(--brand-color-text-link-pressed);
+}
+
 .articleHeading {
   margin: 0;
   /* Two medium gaps separate the title from the text below, while the

website/src/components/brand/styles/github-copilot-app.module.css

@@ -960,6 +960,17 @@
   border-block-start: none;
 }
 
+/* Raw markdown links inherit the UA default blue/purple otherwise, which is
+   too harsh in dark mode; route them through the themed link token instead. */
+.articleSection a {
+  color: var(--brand-color-text-link-rest);
+}
+
+.articleSection a:hover,
+.articleSection a:focus-visible {
+  color: var(--brand-color-text-link-pressed);
+}
+
 .articleHeading {
   margin: 0;
   margin-block-end: var(--base-size-16);