Merge branch 'fix/mermaid-theme-change'

Author: ThisIs-Developer

styles.css

@@ -73,12 +73,17 @@
   padding: 0;
 }
 
+html,
+body {
+  height: 100%;
+  overflow: hidden;
+}
+
 body {
   background-color: var(--bg-color);
   color: var(--text-color);
   /* PERF-021: Removed background-color transition to avoid full-viewport repaint on theme toggle */
   transition: color 0.15s ease;
-  min-height: 100vh;
   font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Hiragino Kaku Gothic ProN", Meiryo, "Malgun Gothic", "Apple SD Gothic Neo", "Segoe UI", Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji";
 }