enhance: improve assistant message rendering and console patching

- Split multi-line assistant messages into separate rendered lines
- Add streaming cursor (▌) indicator for in-progress responses
- Add patchConsole() to intercept System.out/err during TUI mode
- Handle empty assistant message edge case

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

src/main/java/com/claudecode/tui/JinkReplSession.java

@@ -96,6 +96,9 @@ public class JinkReplSession {
         // 启动 jink 渲染
         inkApp = Ink.render(component);
 
+        // 拦截 System.out/err，防止日志干扰 TUI
+        inkApp.patchConsole();
+
         // 阻塞等待退出
         inkApp.waitUntilExit();