refactor(NumericUpDown): template-bind clear icon, motion, and font-size parts; align the theme-first rule wording

AGENTS.md

@@ -115,7 +115,16 @@ Detailed AI collaboration rules live in [docs/engineering/contributing/agent-gui
 - Treat AOT compatibility as a first-class design constraint for new features and bug fixes.
 - Verify with tests or publish checks that match the risk of the change.
 - Follow the mandatory Superpowers workflow before any creation, change, implementation, or bug fix: invoke `superpowers:using-superpowers`, then route through `superpowers:brainstorming` (new features/components), `superpowers:systematic-debugging` (bugs), `superpowers:test-driven-development` (implementation), `superpowers:writing-plans`/`superpowers:executing-plans` (multi-step work), and `superpowers:verification-before-completion` (before claiming done). Never skip a skill that could apply; only an explicit user instruction may narrow it.
-- Prefer declaring template/style bindings (RenderTransform, Transitions, template-part properties, pseudo-class driven setters) in AXAML ControlThemes whenever a selector/Setter can reach the target, the runtime behavior is identical, and there is no measurable performance cost. Fall back to code-behind binding only when the ControlTheme cannot express it — for example targets inside a Content subtree beyond the `/template/` chain, internal members invisible to compiled bindings, runtime-computed values, or AOT-unsafe reflection — and state the reason in a code comment. When an existing code-side binding can be migrated to a ControlTheme with identical behavior and performance, migrate it as part of any change that touches the file. Note: `Transitions` must be declared in ControlTheme style setters, never directly inside ControlTemplate content (template build has no clock attached and throws NRE).
+
+## 主题绑定优先强约束（本项目生效）
+
+1. **ControlTheme 优先**：Avalonia 控件的模板/样式类绑定（含 RenderTransform、Transitions、模板部件属性、伪类驱动的 Setter 等），只要同时满足以下全部条件，必须优先放在 AXAML ControlTheme 中声明，禁止先写成代码绑定：
+   - ControlTheme 能表达该绑定（选择器 / Setter / 模板绑定可达目标元素）；
+   - 逻辑效果与代码绑定完全一致（触发时机、状态条件、取值、动画行为）；
+   - 性能无可测量差异。
+2. **代码绑定是兜底**：仅当 ControlTheme 无法完成时（如目标元素在 Content 子树跨不进 `/template/` 链、依赖 internal 成员而 XAML 编译绑定不可见、目标值为运行时计算值、AOT 约束禁止反射绑定等），才允许放到控件代码中绑定，且必须在代码注释中写明 ControlTheme 不可行的具体原因。
+3. **迁移义务**：发现既有的代码绑定实际上可以等价迁移到 ControlTheme 时，在触及该文件的改动中一并迁移，不留“下次再说”。
+4. **声明位置边界**：`Transitions` 必须声明在 ControlTheme 的 style setter 中，禁止直接写在 ControlTemplate 内容里——模板构建期元素尚未挂载 clock，会抛 NullReferenceException。
 
 ## Common Commands
 

docs/controls/desktop/data-entry/numeric-up-down/changelog.md

@@ -13,6 +13,7 @@
 - Behavior
   - Restore the floating-handle hover shift for the suffix group: since the suffix group moved into the spinner content segment (outside the decorated box `ContentRightAddOn` slot), the animated `ButtonSpinnerDecoratedBox.ContentRightShift` no longer reached it through the template. The transform (`translateX`) and its `TransformOperationsTransition` are declared in the ControlTheme behind the `IsMotionEnabled` gate; `NumericUpDown` code only reacts to the decorated box hover state and replaces the `RenderTransform` value, which arms the transition. Re-mirroring the animated property frame by frame was rejected: the per-frame relay fights the render clock and shows up as a one-frame jump ("flicker") when the pointer re-enters quickly. Note: `Transitions` cannot be declared directly inside ControlTemplate content — the template build has no clock attached and throws NRE — so the transition lives in a style setter.
   - Fix `InnerLeftContent` never rendering: the prefix presenter lives in a `ButtonSpinner.InnerLeftContent` property-element subtree where `TemplatedParent` never propagates, so its `TemplateBinding`s stayed dead. The presenter is now named `PART_InnerLeftContentPresenter` and relays `InnerLeftContent` / `InnerLeftContentTemplate` in code, matching the suffix presenter pattern.
+  - Consolidate part bindings into the ControlTheme where the template can express them: the clear button's `Icon` / `IsMotionEnabled`, the text box's `IsCustomFontSize`, and the inner-right presenter's `Content` / `ContentTemplate` (already template-bound since the suffix group moved into direct template content) no longer go through code relays. The remaining code relays are exactly the ones the ControlTheme cannot express: the prefix presenter's property-element subtree (dead `TemplatedParent`), and the clear button's visibility from the internal direct property `IsEffectiveShowClearButton`.
   - Move the `clear` button from the suffix addon row into the input segment (right edge of the text area, before the spinner action buttons) in both mode templates; its semantic route simplifies to `/template/ .semantic-clear`.
   - Keep the inner-right content (`suffix` group) attached after the clear button inside the input segment in both mode templates, so `clear`, the user suffix content and the spinner action buttons keep consistent spacing; the `suffix` semantic route simplifies to `/template/ .semantic-suffix`. The Spinner mode adds an 8px inset between the suffix group and the action-button divider, whose content frame has no padding of its own.
   - Relay the owner `BorderBrush` onto the input frame as a local value (mirroring the shared `AbstractTextInput` behavior and antd `styles.root.borderColor`), so application root border customization wins over the frame state machine; clearing the owner value restores the themed border.

src/AtomUI.Desktop.Controls/NumericUpDown/NumericUpDown.cs

@@ -488,10 +488,9 @@ public partial class NumericUpDown : AvaloniaNumericUpDown,
 
         if (e.NameScope.Find<InputClearIconButton>("PART_ClearButton") is { } clearButton)
         {
-            _templatePartBindings.Add(BindUtils.RelayBind(this, ClearIconProperty, clearButton,
-                AbstractIconButton.IconProperty));
-            _templatePartBindings.Add(BindUtils.RelayBind(this, IsMotionEnabledProperty, clearButton,
-                AbstractIconButton.IsMotionEnabledProperty));
+            // Only the visibility relay stays in code: IsEffectiveShowClearButton is an internal
+            // direct property, invisible to compiled template bindings. Icon and IsMotionEnabled
+            // are template-bound in the ControlTheme.
             _templatePartBindings.Add(BindUtils.RelayBind(this, IsEffectiveShowClearButtonProperty, clearButton,
                 Visual.IsVisibleProperty));
         }
@@ -506,19 +505,9 @@ public partial class NumericUpDown : AvaloniaNumericUpDown,
                 innerLeftContent, ContentPresenter.ContentTemplateProperty));
         }
 
-        if (e.NameScope.Find<ContentPresenter>("PART_InnerRightContentPresenter") is { } innerRightContent)
-        {
-            _templatePartBindings.Add(BindUtils.RelayBind(this, InnerRightContentProperty, innerRightContent,
-                ContentPresenter.ContentProperty));
-            _templatePartBindings.Add(BindUtils.RelayBind(this, InnerRightContentTemplateProperty,
-                innerRightContent, ContentPresenter.ContentTemplateProperty));
-        }
-
-        if (e.NameScope.Find<TextBox>("PART_TextBox") is { } textBox)
-        {
-            _templatePartBindings.Add(BindUtils.RelayBind(this, IsCustomFontSizeProperty, textBox,
-                TextBox.IsCustomFontSizeProperty));
-        }
+        // InnerRightContent / InnerRightContentTemplate and the text box IsCustomFontSize are
+        // template-bound in the ControlTheme (the parts sit in direct template content where
+        // TemplatedParent propagates), so no code relay is needed for them.
 
         // The suffix group renders inside the spinner content segment, outside the decorated box's
         // ContentRightAddOn slot, so the floating-handle shift no longer reaches it through the

src/AtomUI.Desktop.Controls/NumericUpDown/Themes/NumericUpDownTheme.axaml

@@ -49,6 +49,8 @@
                                 Name="PART_ClearButton"
                                 Classes.semantic-clear="True"
                                 VerticalAlignment="Center"
+                                Icon="{TemplateBinding ClearIcon}"
+                                IsMotionEnabled="{TemplateBinding IsMotionEnabled}"
                                 IsPassthroughMouseEvent="False" />
                             <atom:AddOnContentPresenter
                                 Name="PART_InnerRightContentPresenter"
@@ -75,6 +77,7 @@
                             AcceptsReturn="False"
                             DataValidationErrors.Errors="{TemplateBinding DataValidationErrors.Errors}"
                             SizeType="Custom"
+                            IsCustomFontSize="{TemplateBinding IsCustomFontSize}"
                             IsReadOnly="{TemplateBinding IsReadOnly}"
                             Text="{TemplateBinding Text, Mode=TwoWay}"
                             PlaceholderText="{TemplateBinding PlaceholderText}"
@@ -131,6 +134,8 @@
                                     Name="PART_ClearButton"
                                     Classes.semantic-clear="True"
                                     VerticalAlignment="Center"
+                                    Icon="{TemplateBinding ClearIcon}"
+                                    IsMotionEnabled="{TemplateBinding IsMotionEnabled}"
                                     IsPassthroughMouseEvent="False" />
                                 <atom:AddOnContentPresenter
                                     Name="PART_InnerRightContentPresenter"
@@ -157,6 +162,7 @@
                                 AcceptsReturn="False"
                                 DataValidationErrors.Errors="{TemplateBinding DataValidationErrors.Errors}"
                                 SizeType="Custom"
+                                IsCustomFontSize="{TemplateBinding IsCustomFontSize}"
                                 IsReadOnly="{TemplateBinding IsReadOnly}"
                                 Text="{TemplateBinding Text, Mode=TwoWay}"
                                 TextAlignment="Center"