feat(ui): 主菜单/暂停菜单屏幕状态机——中文标题「年糕历险记」、按钮点击、Esc 暂停（烟雾测试 10 秒无崩溃）

cmd/client/input.go

@@ -31,6 +31,12 @@ type inputState struct {
 	breakHeld  bool
 	placeDown  bool
 	selectSlot int // -1 无
+
+	// 鼠标与 UI 事件（UI与输入.md §6 屏幕交互）
+	cursorX, cursorY float64
+	clickX, clickY   float32
+	clicked          bool
+	escPressed       bool
 }
 
 // newInputState 创建输入状态并注册回调。
@@ -63,7 +69,7 @@ func (in *inputState) keyCallback(_ *glfw.Window, key glfw.Key, _ int, action gl
 		in.sprint = down
 	case glfw.KeyEscape:
 		if action == glfw.Press {
-			in.win.SetShouldClose(true)
+			in.escPressed = true // 暂停/继续由屏幕状态机处理
 		}
 	case glfw.Key1, glfw.Key2, glfw.Key3, glfw.Key4, glfw.Key5, glfw.Key6, glfw.Key7, glfw.Key8, glfw.Key9:
 		if action == glfw.Press {
@@ -78,6 +84,9 @@ func (in *inputState) mouseButtonCallback(_ *glfw.Window, button glfw.MouseButto
 	case glfw.MouseButtonLeft:
 		if action == glfw.Press {
 			in.breakDown = true
+			in.clicked = true
+			in.clickX = float32(in.cursorX)
+			in.clickY = float32(in.cursorY)
 		}
 		in.breakHeld = action != glfw.Release
 	case glfw.MouseButtonRight:
@@ -89,6 +98,7 @@ func (in *inputState) mouseButtonCallback(_ *glfw.Window, button glfw.MouseButto
 
 // cursorCallback 鼠标移动：yaw/pitch 累积（渲染.md §2 主线程消费）。
 func (in *inputState) cursorCallback(_ *glfw.Window, x, y float64) {
+	in.cursorX, in.cursorY = x, y
 	if in.firstMouse {
 		in.lastX, in.lastY = x, y
 		in.firstMouse = false