Add RepositionThemeTransition to sample pages for smoother layout updates

[Zakariathr22]

Important

Do not merge until this is resolved

Description

Added RepositionThemeTransition to sample pages with many control examples for smoother layout updates.

Motivation and Context

Improves visual consistency.

How Has This Been Tested?

Manually verified across affected sample pages to ensure transitions apply correctly without breaking layout.

Screenshots (if appropriate):

Before

After

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

[Saharsh979]

/azp run

[Saharsh979]

The PR description lacks the rationale behind why RepositionThemeTransition is added, which could confuse maintainers unfamiliar with it. Feel free to add more details along with the Before vs After Screenshot to give a visual sense of the improvement you're introducing.

[Saharsh979]

Modifying 74 files manually is an anti-pattern for maintainability.
Is there a way to avoid/minimize this? Can we think of adding a shared style for the applicable pages?

[niels9001]

Agreed, an ItemPageRootStackPanelStyle (or something like that) that has these transitions included might be helpful - also in case we want to do add other standard properties in the future

[Zakariathr22]

@Saharsh979 @niels9001 I have another idea

I introduced a new SamplePage base class that automatically applies a RepositionThemeTransition to the root Panel of any derived page. This way, we don’t need to manually add transitions on pages with many examples (it’s handled consistently at the base level)
You can already see this applied to the BindingPage in this change 5b5f8c9

Should we extend this behaviour to all sample pages?

[niels9001]

Would love to get @marcelwgn's opinion here

[Zakariathr22]

The PR description lacks the rationale behind why RepositionThemeTransition is added, which could confuse maintainers unfamiliar with it. Feel free to add more details along with the Before vs After Screenshot to give a visual sense of the improvement you're introducing.

Done!

[AndrewKeepCoding]

If we are reducing code for this implementation, we can create a style for these StackPanels.

<Style x:Key="StackPanelWithRepositionThemeTransitionStyle" TargetType="StackPanel">
    <Setter Property="ChildrenTransitions">
        <Setter.Value>
            <TransitionCollection>
                <RepositionThemeTransition />
            </TransitionCollection>
        </Setter.Value>
    </Setter>
    <Setter Property="Spacing" Value="12"/>
</Style>