align command palette prefix > to left when visible

[bhaskarshankarling]

Fixes the clear button to clear the typed command not clickable in the
command palette.

• From the primary investigation it looked like the TextBlock element
  introduced in Swap the command palette modes for the prefix > #7935 was somehow blocking (appearing on top of) the
  clear button.
• It was also blocking the command palette input field from being able
  to access which was preventing the text in the input field from being
  selected and the cursor would still show as pointer cursor instead
  of a text selection cursor
• Adding HorizontalAlignment="Left" property to the above-mentioned
  TextBlock element fixed the issue.

Validation Steps Performed

• Created the Dev build for x64 in Visual Studio and verified the
  functionality manually.

Closes #8220

[ghost]

All CLA requirements met.

[zadjii-msft]

what the heck

Testing this out, it definitely works, but like, why?

^{(That's a rhetorical "why" - I don't really need an explanation)}

[bhaskarshankarling]

@zadjii-msft It may be possible that the solution could be bit out of normal as I have zero working experience in building Windows applications, nuget, XAML, C++ codebase, PowerShell or Visual Studio project but since I rely heavily on Windows Terminal (and WSL2) for Ruby on Rails and JavaScript projects I really appreciate you folks' effort on making Windows Terminal better everyday. So, I thought of contributing as much as I can even though I don't have previous working knowledge in these tech stack.

So coming back to the initial point, I arrived at the solution mostly by git bisect as the solution was working in the previous version and skimming through some docs to understand XAML and Visual Studio projects just enough to understand the repo. So, please suggest if the fix needs to be implemented in a certain way.

On top of all of this, it would be my first ever open source contribution if it makes to main branch. Thank you very much for approving. If possible please share the links to any resource which you consider would be a good place to start with to understand Windows application development ecosystem.

[zadjii-msft]

You did a great job with this, I'll be honest. I don't think I would have intuitively tried the HorizontalAlignment=Left thing, which definitely seems to work here. I don't have all that much XAML experience though, so I guess I don't know how that interacts with the width of the control. So props to you for figuring that out 🎉

[DHowett]

I'm surprised that this was the problem. Good catch!

[ghost]

Hello @DHowett!

Because this pull request has the AutoMerge label, I will be glad to assist with helping to merge this pull request once all check-in policies pass.

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[ghost]

🎉Windows Terminal Preview v1.5.3242.0 has been released which incorporates this pull request.:tada:

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