[feature] Cancel SelectionPrompt on Esc (Fixes #851)

[nimobit]

Fixes #851

Changes

• Added logic in SelectionPrompt to cancel when Escape key is pressed
• Returns null to match expected behavior
• Added unit test to simulate Escape key press and assert OperationCanceledException

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Checklist

• I have read the Contribution Guidelines
• I have commented on the issue and discussed the intended changes
• All newly added code is adequately covered by tests
• All existing tests are still running without errors
• No documentation changes required

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This is my first pull request to this project.
I'm open to any suggestions or feedback to improve it!

[nimobit]

@microsoft-github-policy-service agree

[patriksvensson]

Hi!

Thanks so much for taking the time to submit this PR.
I really appreciate the contribution!

Unfortunately, I haven’t had the capacity to review this in a timely manner, and since it was opened, the repository has changed significantly. Because of that, this PR is no longer in a state where it can be reviewed or merged as-is. This is not your fault, but mine, and I'm sorry about this.

I’m going to close it for now to help keep things tidy. That said, if you’re still interested in contributing, please feel free to open a new pull request that’s up to date with the current state of the repository, and I’ll be happy to take a look when I can. I'll promise I'll do better this time around.

Thanks again for your work and for your interest in the project!