fix(slider): optimize tick label alignment to prevent text overflow

Add isFirst/isLast properties and effectiveHorizontalAlignment to align
first/last tick labels outward (left for first, right for last), preventing
text overflow at slider edges. Use negative margins to offset label padding
for better visual alignment with tick marks. Add null safety checks and
documentation comments.

为 SliderTipItem 添加首尾刻度标签特殊对齐逻辑，首刻度左对齐、尾刻度右对齐，
防止文本在滑块边缘溢出。使用负边距抵消标签 padding，使文字与刻度对齐。
添加空值安全检查和文档注释。

Log: 优化滑块刻度标签对齐，防止边缘文本溢出
PMS: BUG-305223
Influence: TipsSlider 的首尾刻度标签现在会自动向外对齐，提升视觉效果并防止文本溢出。

Author: add-uos

qt6/src/qml/SliderTipItem.qml

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: 2022 UnionTech Software Technology Co., Ltd.
+// SPDX-FileCopyrightText: 2022 - 2026 UnionTech Software Technology Co., Ltd.
 //
 // SPDX-License-Identifier: LGPL-3.0-or-later
 
@@ -14,6 +14,21 @@ Control {
     readonly property int direction: parent.parent.tickDirection
     readonly property bool horizontal: parent.parent.children[0].horizontal
     property bool highlight
+    readonly property bool isFirst: {
+        var ticks = parent.parent.ticks || []
+        return ticks.indexOf(control) === 0
+    }
+    readonly property bool isLast: {
+        var ticks = parent.parent.ticks || []
+        return ticks.indexOf(control) === ticks.length - 1
+    }
+    // Align first/last tick labels outward to prevent text overflow at slider edges
+    readonly property int effectiveHorizontalAlignment: {
+        if (!horizontal) return textHorizontalAlignment
+        if (isFirst) return Text.AlignLeft
+        if (isLast) return Text.AlignRight
+        return textHorizontalAlignment
+    }
 
     property D.Palette tickColor: DS.Style.slider.tick.background
     property D.Palette textColor: highlight ? DS.Style.checkedButton.text: DS.Style.button.text
@@ -36,16 +51,16 @@ Control {
         active: text.length !== 0
         anchors {
             top: horizontal ? (TipsSlider.TickDirection.Back === direction ? __rect.bottom : undefined) : undefined
-            topMargin: horizontal && (TipsSlider.TickDirection.Back === direction) ? DS.Style.slider.tick.vPadding : undefined
+            topMargin: horizontal && (TipsSlider.TickDirection.Back === direction) ? DS.Style.slider.tick.vPadding : -DS.Style.slider.tick.vPadding
             bottom: horizontal ? (TipsSlider.TickDirection.Front === direction ? __rect.top : undefined) : undefined
-            bottomMargin: horizontal && (TipsSlider.TickDirection.Front === direction) ? DS.Style.slider.tick.vPadding : undefined
-            left: horizontal ? (Text.AlignLeft === textHorizontalAlignment ? __rect.left : undefined)
+            bottomMargin: horizontal && (TipsSlider.TickDirection.Front === direction) ? DS.Style.slider.tick.vPadding : -DS.Style.slider.tick.vPadding
+            left: horizontal ? (Text.AlignLeft === effectiveHorizontalAlignment ? __rect.left : undefined)
                              : (TipsSlider.TickDirection.Back === direction ? __rect.right : undefined)
-            leftMargin: !horizontal && TipsSlider.TickDirection.Back === direction ? DS.Style.slider.tick.hPadding : undefined
-            right: horizontal ? (Text.AlignRight === textHorizontalAlignment ? __rect.right : undefined)
+            leftMargin: !horizontal && TipsSlider.TickDirection.Back === direction ? DS.Style.slider.tick.hPadding : -DS.Style.slider.tick.hPadding
+            right: horizontal ? (Text.AlignRight === effectiveHorizontalAlignment ? __rect.right : undefined)
                               : (TipsSlider.TickDirection.Front === direction ? __rect.left : undefined)
-            rightMargin: !horizontal && TipsSlider.TickDirection.Front === direction ? DS.Style.slider.tick.hPadding : undefined
-            horizontalCenter: horizontal && Text.AlignHCenter === textHorizontalAlignment ? __rect.horizontalCenter : undefined
+            rightMargin: !horizontal && TipsSlider.TickDirection.Front === direction ? DS.Style.slider.tick.hPadding : -DS.Style.slider.tick.hPadding
+            horizontalCenter: horizontal && Text.AlignHCenter === effectiveHorizontalAlignment ? __rect.horizontalCenter : undefined
             verticalCenter: horizontal ? undefined : __rect.verticalCenter
         }
 
@@ -55,7 +70,7 @@ Control {
             leftPadding: rightPadding
             topPadding: highlight ?  DS.Style.slider.tick.vPadding : 0
             bottomPadding: topPadding
-            horizontalAlignment: textHorizontalAlignment
+            horizontalAlignment: control.effectiveHorizontalAlignment
             verticalAlignment: Text.AlignVCenter
             palette.windowText: control.D.ColorSelector.textColor
             background: Loader {