Backport of #26491 to release/v7.6

Triggered by @adityapatwardhan on behalf of @daxian-dbw

Original CL Label: CL-General

/cc @PowerShell/powershell-maintainers

Impact

REQUIRED: Choose either Tooling Impact or Customer Impact (or both). At least one checkbox must be selected.

Tooling Impact

• Required tooling change
• Optional tooling change (include reasoning)

Customer Impact

• Customer reported
• Found internally

Fixes critical SSH connection hangs on Windows. When running Invoke-Command -HostName or New-PSSession -HostName on Windows, PowerShell would hang indefinitely due to pipe client handles not being closed after creating the ssh.exe process. This prevents the stdout/stderr reader threads from completing when SSH exits.

Regression

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• Yes
• No

This is not a regression.

Testing

Original PR added tests to verify PowerShell doesn't hang on SSH connections to non-existent hosts. Backport verified by running the new tests on release/v7.6 branch and confirming the fix resolves the Windows-specific SSH hang issue.

Risk

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• High
• Medium
• Low

Medium risk - affects SSH remoting functionality which is commonly used, but the fix is well-scoped to handle cleanup and has comprehensive test coverage. The change only affects the Windows-specific SSH connection code path.