feat(ai-notice): Hide empty AI notice elements

Add CSS rule to hide .ai-notice elements when empty to prevent unwanted
visual gaps. Enhances UI consistency and avoids displaying superfluous
containers. Also update post metadata to indicate AI-generated content,
improving transparency for readers.

Author: jiacai2050

assets/style.css

@@ -832,6 +832,10 @@ blockquote p {
 
 /* -- AI Notice -- */
 
+.ai-notice:empty {
+  display: none;
+}
+
 .ai-notice {
   margin: 1.5rem 0;
   padding: 0.875rem 1.25rem;

content/post/2026-04-16-zig-stm32f103-booting.smd

@@ -4,6 +4,9 @@
 .author = "maldus512 (翻译)",
 .layout = "post.shtml",
 .draft = false,
+.custom = {
+  .ai_generated = true,
+},
 ---
 
 > 原文：https://maldus512.medium.com/zig-bare-metal-programming-on-stm32f103-booting-up-b0ecdcf0de35