fix: Invoke-DataverseSql doesn't respond to CTRL+C

[Copilot]

Description

Invoke-DataverseSql ignored CTRL+C during query execution, only responding after results began streaming. The cmdlet's StopProcessing() method created a cancellation token but never passed it to the underlying SQL4CDS engine.

Changes Made

• Pass _userCancellationCts.Token to ExecuteReaderAsync() to enable query cancellation
• Add IsCanceled check before accessing task result to handle graceful cancellation
• Remove Task.Run wrapper (unnecessary - ExecuteReaderAsync already returns a Task)
• Remove outdated comment claiming SQL4CDS lacks cancellation support

Key change:

// Before
Task<DbDataReader> task = Task.Run(() => _command.ExecuteReaderAsync());

// After  
Task<DbDataReader> task = _command.ExecuteReaderAsync(_userCancellationCts.Token);

Testing

• Build succeeds with no errors
• Manual testing with long-running queries to verify CTRL+C responsiveness

Checklist

• Code follows the project's coding conventions
• Documentation updated (if needed)
• Tests added/updated (if needed)
• PR title uses conventional commit format (REQUIRED)

Original prompt

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This section details on the original issue you should resolve

<issue_title>[BUG] Invoke-dataversesql doesn't respond to CTRL+C (until results start streaming?)</issue_title>
<issue_description>### Description

Steps to Reproduce

Expected Behavior

Actual Behavior

PowerShell version

Module Version

No response

Additional Context

No response

Checklist

• I have tried the latest version of the module
• I have searched for similar issues and couldn't find any
• I have included all the information needed to reproduce the issue</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [BUG] Invoke-dataversesql doesn't respond to CTRL+C (until results start streaming?) #1409

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