feat(settings-ui): animate update activity banner

[Niels Laute (niels9001)]

Summary of the Pull Request

Animates the Settings update activity banner when it appears and is dismissed. The surface rises into place with a subtle fade, then fades and moves down when closed.

PR Checklist

• Communication: Discussed and iterated on the behavior with a core contributor
• Tests: The Settings UI project builds successfully and the animation was manually verified
• Localization: No end-user-facing strings were added or changed

Detailed Description of the Pull Request / Additional comments

• Adds Toolkit Implicit.ShowAnimations and Implicit.HideAnimations directly to the root UpdateActivityControl.
• Animating the root control keeps the Shell layout stable while WinUI retains the outgoing visual for the hide transition.
• Uses cubic easing with a 250 ms rise/200 ms fade on show and a 180 ms drop/200 ms fade on hide.
• Keeps the implementation entirely in UpdateActivityControl.xaml with no code-behind changes.

Validation Steps Performed

• Built src\settings-ui\Settings.UI\PowerToys.Settings.csproj in x64 Debug using tools\build\build.ps1.
• Launched D:\PowerToys\x64\Debug\WinUI3Apps\PowerToys.Settings.exe directly.
• Opened the update activity from the Home dashboard and verified both the show and dismiss transitions.

[github-actions]

🧭 PR intake

Visual evidence: Required — The pull request changes product UI files, so reviewers need to see the visible result. Visual evidence is currently missing.

Recommendation

Link the issue this PR fixes using a closing keyword such as Closes #123.

Author action

Niels Laute (@niels9001), please update the following before review:

• Add a screenshot, GIF, or video to the PR description so reviewers can validate the visible change.

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If there is no author response within 7 days, this PR will be automatically closed.

Automated PR intake; PowerToys maintainers make final decisions.

[Jiří Polášek (jiripolasek)]

Niels Laute (@niels9001) Popup visibility change is animated, and it attracts attention when it shows. The remaining gap is when the popup is already visible when the window is created - no change in visibility state means no animation.

[Jiří Polášek (jiripolasek)]

Puppy popup? You can see how happy it is to see you...

Screen.Recording.2026-09-04.190322.mp4