fix: usa ASCII semplice invece di box drawing Unicode

- Compatibilità migliore con terminali diversi
- Caratteri = e - invece di ╔ ╗ ╚ ╝

terminal_ui.py

@@ -82,18 +82,14 @@ class TerminalUI:
         # Clear screen
         sys.stdout.write("\033[2J\033[H")
         
-        # Header
-        header_color = "\033[1;36m"
+        # Header - ASCII semplice per compatibilità
+        cyan = "\033[1;36m"
         yellow = "\033[1;33m"
         
-        line = "═" * (self.cols - 4)
-        sys.stdout.write(f"{header_color}╔{line}╗{reset}\n")
-        
-        title = " LangCode Agent "
-        title_pos = (self.cols - len(title)) // 2
-        sys.stdout.write(f"{header_color}║{reset}" + " " * title_pos + f"{yellow}{title}{reset}" + " " * (self.cols - title_pos - len(title) - 3) + f"{header_color}║{reset}\n")
-        
-        sys.stdout.write(f"{header_color}╚{line}╝{reset}\n")
+        title = "[ LangCode Agent ]"
+        sys.stdout.write(f"{cyan}========================================{reset}\n")
+        sys.stdout.write(f"{cyan}={reset}        {yellow}{title}{reset}         {cyan}={reset}\n")
+        sys.stdout.write(f"{cyan}========================================{reset}\n\n")
         
         # Contenuto
         visible = self.rows - 7