fix: 命令描述统一为英文+修复/history双斜杠bug

- CompactCommand: 中文描述改为英文
- HistoryCommand: 中文描述改为英文 + name()去掉多余的/前缀

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/main/java/com/claudecode/command/impl/CompactCommand.java

@@ -39,7 +39,7 @@ public class CompactCommand implements SlashCommand {
 
     @Override
     public String description() {
-        return "用AI摘要压缩对话上下文";
+        return "Compact conversation context with AI summary";
     }
 
     @Override

src/main/java/com/claudecode/command/impl/HistoryCommand.java

@@ -14,12 +14,12 @@ public class HistoryCommand implements SlashCommand {
 
     @Override
     public String name() {
-        return "/history";
+        return "history";
     }
 
     @Override
     public String description() {
-        return "列出保存的对话历史";
+        return "List saved conversation history";
     }
 
     @Override