feat(changelog): 使用统一的 CHANGELOG_HEADER 常量生成标准化头部

src/commands/changelog.rs

@@ -162,8 +162,10 @@ impl ChangelogCommand {
         if output_path.exists() {
             let existing = std::fs::read_to_string(&output_path)?;
             let new_content = if existing.is_empty() {
-                format!("# Changelog\n\n{}", changelog)
-            } else {
+                format!("{}{}", CHANGELOG_HEADER, changelog)
+            } else if existing.starts_with(CHANGELOG_HEADER) {
+                format!("{}{}", CHANGELOG_HEADER, changelog)
+            } else if existing.starts_with("# Changelog") {
                 let lines: Vec<&str> = existing.lines().collect();
                 let mut header_end = 0;
                 
@@ -181,10 +183,12 @@ impl ChangelogCommand {
                 let rest = lines[header_end..].join("\n");
                 
                 format!("{}\n{}\n{}", header, changelog, rest)
+            } else {
+                format!("{}{}", CHANGELOG_HEADER, changelog)
             };
             std::fs::write(&output_path, new_content)?;
         } else {
-            let content = format!("# Changelog\n\n{}", changelog);
+            let content = format!("{}{}", CHANGELOG_HEADER, changelog);
             std::fs::write(&output_path, content)?;
         }