feat: undo/redo added

modules/ui/src/main/scala/de/nowchess/ui/terminal/TerminalUI.scala

@@ -20,7 +20,7 @@ class TerminalUI(engine: GameEngine) extends Observer:
         print(Renderer.render(e.board))
         e.capturedPiece.foreach: cap =>
           println(s"Captured: $cap on ${e.toSquare}")
-        println(s"${e.turn.label}'s turn. Enter move (or 'quit'/'q' to exit):")
+        printPrompt(e.turn)
 
       case e: CheckDetectedEvent =>
         println(s"${e.turn.label} is in check!")
@@ -36,13 +36,13 @@ class TerminalUI(engine: GameEngine) extends Observer:
         print(Renderer.render(e.board))
 
       case e: InvalidMoveEvent =>
-        println(s"Invalid move: ${e.reason}")
+        println(s"⚠️  ${e.reason}")
 
       case e: BoardResetEvent =>
         println("Board has been reset to initial position.")
         println()
         print(Renderer.render(e.board))
-        println(s"${e.turn.label}'s turn. Enter move (or 'quit'/'q' to exit):")
+        printPrompt(e.turn)
 
   /** Start the terminal UI game loop. */
   def start(): Unit =
@@ -52,7 +52,7 @@ class TerminalUI(engine: GameEngine) extends Observer:
     // Show initial board
     println()
     print(Renderer.render(engine.board))
-    println(s"${engine.turn.label}'s turn. Enter move (or 'quit'/'q' to exit):")
+    printPrompt(engine.turn)
 
     // Game loop
     while running do
@@ -62,11 +62,16 @@ class TerminalUI(engine: GameEngine) extends Observer:
           running = false
           println("Game over. Goodbye!")
         case "" =>
-          println("Please enter a valid move.")
+          printPrompt(engine.turn)
         case _ =>
           engine.processUserInput(input)
 
     // Unsubscribe when done
     engine.unsubscribe(this)
 
+  private def printPrompt(turn: de.nowchess.api.board.Color): Unit =
+    val undoHint = if engine.canUndo then " [undo]" else ""
+    val redoHint = if engine.canRedo then " [redo]" else ""
+    print(s"${turn.label}'s turn. Enter move (or 'quit'/'q' to exit)$undoHint$redoHint: ")
+
 end TerminalUI