feat: 添加恢复代码块占位符的功能，优化文本处理逻辑

src/channels/feishu.rs

@@ -1931,15 +1931,24 @@ impl FeishuChannel {
             );
         }
 
+        /// Restore all code block placeholders in the given text.
+        fn restore_code_blocks(text: &str, code_blocks: &[String]) -> String {
+            let mut result = text.to_string();
+            for (i, cb) in code_blocks.iter().enumerate() {
+                result = result.replace(&format!("\x00CODE{}\x00", i), cb);
+            }
+            result
+        }
+
         let mut elements: Vec<serde_json::Value> = Vec::new();
         let mut last_end = 0;
 
         for m in patterns.heading_re.find_iter(&protected) {
-            let before = &protected[last_end..m.start()].trim();
+            let before = protected[last_end..m.start()].trim();
             if !before.is_empty() {
                 elements.push(serde_json::json!({
                     "tag": "markdown",
-                    "content": before
+                    "content": restore_code_blocks(before, &code_blocks)
                 }));
             }
 
@@ -1963,14 +1972,9 @@ impl FeishuChannel {
 
         let remaining = protected[last_end..].trim();
         if !remaining.is_empty() {
-            // Restore code blocks
-            let mut final_content = remaining.to_string();
-            for (i, cb) in code_blocks.iter().enumerate() {
-                final_content = final_content.replace(&format!("\x00CODE{}\x00", i), cb);
-            }
             elements.push(serde_json::json!({
                 "tag": "markdown",
-                "content": final_content
+                "content": restore_code_blocks(remaining, &code_blocks)
             }));
         }