fix(a11y): improve chapter description text contrast to meet WCAG AA (#136)

Chapter hint text on title browse pages used text-gray-400 which fails
WCAG AA contrast (4.39:1 on warm-white, needs 4.5:1). Changed to
text-slate (dark mode: text-gray-400) which provides 6.48:1+ contrast.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: williamzujkowski

apps/web/src/pages/browse/[title].astro

@@ -182,7 +182,7 @@ const chapters: ChapterView[] = sortedChapters.map(([chapterNum, chapterEntries]
               Ch. {ch.chapterNum}
             </a>
             {ch.chapterHint && (
-              <span class="truncate text-xs text-gray-400 dark:text-gray-600">&mdash; {ch.chapterHint}</span>
+              <span class="truncate text-xs text-slate dark:text-gray-400">&mdash; {ch.chapterHint}</span>
             )}
           </span>
           <span class="ml-auto flex items-center gap-2 text-xs text-gray-400">