fix: 重写通道勾选逻辑，clicked信号直接驱动显示/隐藏

- 改用clicked信号代替toggled，避免程序改动误触发
- 初始默认不勾选(setChecked(false))
- 勾选框样式优化：勾上蓝底，不勾灰色
- 勾选立即update()刷新图例+曲线

mainwindow.cpp

@@ -109,15 +109,17 @@ void MainWindow::setupUi()
     channelLayout->setSpacing(2);
 
     for (int i = 0; i < 16; ++i) {
-        QCheckBox *check = new QCheckBox(QString("ch%1").arg(i));
-        check->setChecked(true);
+        QCheckBox *check = new QCheckBox(QString("CH%1").arg(i+1));
+        check->setChecked(false);
         check->setStyleSheet(
             "QCheckBox { color: #aaa; font-size: 11px; spacing: 4px; }"
-            "QCheckBox::indicator { width: 12px; height: 12px; }"
-            "QCheckBox::indicator:checked { background: #3498db; }"
+            "QCheckBox::indicator { width: 14px; height: 14px; }"
+            "QCheckBox::indicator:checked { background-color: #3498db; border: 1px solid #2980b9; }"
+            "QCheckBox::indicator:unchecked { background-color: #333; border: 1px solid #555; }"
         );
-        connect(check, &QCheckBox::toggled, this, [this, i](bool checked) {
-            onToggleChannel(i, checked);
+        connect(check, &QCheckBox::clicked, this, [this, i](bool checked) {
+            m_plotWidget->setChannelVisible(i, checked);
+            m_plotWidget->update();
         });
         channelLayout->addWidget(check);
         m_channelChecks.append(check);