CmdPal: Fix updating primary command and context menu and app icons (#42155)

## Summary of the Pull Request

This PR fixes three issues in one go:
- Restores missing icons in app context menus.
- Fixes propagation of changes from a command item to the context menu
item for the primary action.
- Ensures the context menus stay in sync when underlying command items
change.

Details:
- Correctly propagates updates of name, icon, and subtitle from a
command item to its primary command
(`CommandItemViewModel._defaultCommandContextItemViewModel`).
- Correctly propagate updates of command's name to title
(`CommandItem.ctor`).
- Fixes icon loading for application items: `AppCommand` no longer loads
an app icon by default but instead relies on the caller to provide one
(since `AppListItem` also handles icon loading).
- Adds a generic fallback icon for apps when an icon cannot be loaded.
- Updates bindings on context menu items to `OneWay`, ensuring the UI
properly reflects item changes.
- Adds a sample that showcases dynamically updated commands (with cats
and dolphins!) to _Samples → List Page Sample Command_.

⚠️ Toolkit changes:
- `CommandItem` won't capture assigned Command's name as its `Title`.
This will allow it to propagate future changes to `Command.Name`.

Pictures? Moving ones!


https://github.com/user-attachments/assets/1a482394-d222-4f7c-9922-bb67d47dc566

<img width="864" height="538" alt="image"
src="https://github.com/user-attachments/assets/12f07b3e-f41c-4c40-a4e5-315f40676c52"
/>


<!-- Please review the items on the PR checklist before submitting-->
## PR Checklist

- [x] Closes: #40946
- [x] Related: #40991 
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

src/modules/cmdpal/Microsoft.CmdPal.UI/Controls/ContextMenu.xaml

@@ -31,7 +31,7 @@
 
             <!--  Template for context items in the context item menu  -->
             <DataTemplate x:Key="DefaultContextMenuViewModelTemplate" x:DataType="coreViewModels:CommandContextItemViewModel">
-                <Grid AutomationProperties.Name="{x:Bind Title}">
+                <Grid AutomationProperties.Name="{x:Bind Title, Mode=OneWay}">
                     <Grid.ColumnDefinitions>
                         <ColumnDefinition Width="32" />
                         <ColumnDefinition Width="*" />
@@ -42,7 +42,7 @@
                         Height="16"
                         Margin="4,0,0,0"
                         HorizontalAlignment="Left"
-                        SourceKey="{x:Bind Icon}"
+                        SourceKey="{x:Bind Icon, Mode=OneWay}"
                         SourceRequested="{x:Bind help:IconCacheProvider.SourceRequested}" />
                     <TextBlock
                         x:Name="TitleTextBlock"
@@ -51,11 +51,11 @@
                         HorizontalAlignment="Left"
                         VerticalAlignment="Center"
                         MaxLines="1"
-                        Text="{x:Bind Title}"
+                        Text="{x:Bind Title, Mode=OneWay}"
                         TextTrimming="WordEllipsis"
                         TextWrapping="NoWrap">
                         <ToolTipService.ToolTip>
-                            <ToolTip Content="{x:Bind Title}" Visibility="{Binding IsTextTrimmed, ElementName=TitleTextBlock, Converter={StaticResource BoolToVisibilityConverter}}" />
+                            <ToolTip Content="{x:Bind Title, Mode=OneWay}" Visibility="{Binding IsTextTrimmed, ElementName=TitleTextBlock, Mode=OneWay, Converter={StaticResource BoolToVisibilityConverter}}" />
                         </ToolTipService.ToolTip>
                     </TextBlock>
                     <TextBlock
@@ -65,13 +65,13 @@
                         VerticalAlignment="Center"
                         Foreground="{ThemeResource MenuFlyoutItemKeyboardAcceleratorTextForeground}"
                         Style="{StaticResource CaptionTextBlockStyle}"
-                        Text="{x:Bind RequestedShortcut, Converter={StaticResource KeyChordToStringConverter}}" />
+                        Text="{x:Bind RequestedShortcut, Mode=OneWay, Converter={StaticResource KeyChordToStringConverter}}" />
                 </Grid>
             </DataTemplate>
 
             <!--  Template for context items flagged as critical  -->
             <DataTemplate x:Key="CriticalContextMenuViewModelTemplate" x:DataType="coreViewModels:CommandContextItemViewModel">
-                <Grid AutomationProperties.Name="{x:Bind Title}">
+                <Grid AutomationProperties.Name="{x:Bind Title, Mode=OneWay}">
                     <Grid.ColumnDefinitions>
                         <ColumnDefinition Width="32" />
                         <ColumnDefinition Width="*" />
@@ -83,7 +83,7 @@
                         Margin="4,0,0,0"
                         HorizontalAlignment="Left"
                         Foreground="{ThemeResource SystemFillColorCriticalBrush}"
-                        SourceKey="{x:Bind Icon}"
+                        SourceKey="{x:Bind Icon, Mode=OneWay}"
                         SourceRequested="{x:Bind help:IconCacheProvider.SourceRequested}" />
                     <TextBlock
                         x:Name="TitleTextBlock"
@@ -93,11 +93,11 @@
                         VerticalAlignment="Center"
                         MaxLines="1"
                         Style="{StaticResource ContextItemTitleTextBlockCriticalStyle}"
-                        Text="{x:Bind Title}"
+                        Text="{x:Bind Title, Mode=OneWay}"
                         TextTrimming="WordEllipsis"
                         TextWrapping="NoWrap">
                         <ToolTipService.ToolTip>
-                            <ToolTip Content="{x:Bind Title}" Visibility="{Binding IsTextTrimmed, ElementName=TitleTextBlock, Converter={StaticResource BoolToVisibilityConverter}}" />
+                            <ToolTip Content="{x:Bind Title, Mode=OneWay}" Visibility="{Binding IsTextTrimmed, ElementName=TitleTextBlock, Mode=OneWay, Converter={StaticResource BoolToVisibilityConverter}}" />
                         </ToolTipService.ToolTip>
                     </TextBlock>
                     <TextBlock
@@ -106,7 +106,7 @@
                         HorizontalAlignment="Right"
                         VerticalAlignment="Center"
                         Style="{StaticResource ContextItemCaptionTextBlockCriticalStyle}"
-                        Text="{x:Bind RequestedShortcut, Converter={StaticResource KeyChordToStringConverter}}" />
+                        Text="{x:Bind RequestedShortcut, Mode=OneWay, Converter={StaticResource KeyChordToStringConverter}}" />
                 </Grid>
             </DataTemplate>