Fix CTRL-C stall issue.

[mitchdenny]

Fixes #10955

I need to do a bit more investigtation to figure out why task cancellation isn't unwinding the dotnet package search process faster but this fixes it on the calling side.

Putting this up so I can validate PR bits in a few different scenarios.

[Copilot]

Pull Request Overview

This PR fixes a CTRL-C stall issue (#10955) where the CLI update notifier was preventing graceful cancellation when users attempted to interrupt the application. The changes implement a timeout-based cancellation strategy to avoid hanging on package search operations.

Key changes:

• Implements early cancellation detection in the update notifier using TaskCompletionSource
• Significantly reduces the update check timeout from 10 seconds to 100 milliseconds
• Removes default parameter values from cancellation token parameters to ensure explicit cancellation handling

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/Aspire.Cli/Utils/CliUpdateNotifier.cs	Adds cancellation-aware logic using TaskCompletionSource and removes default cancellation token parameter
src/Aspire.Cli/Commands/BaseCommand.cs	Reduces update notification timeout from 10 seconds to 100ms and removes default cancellation token parameter

Comments suppressed due to low confidence (1)

[davidfowl]

Running aspire add then ctrl + c never shows me the update. Not a huge deal as run pretty much always works.