Fix Cursor fetch crash path

[ratulsarna]

Summary

• replace the Cursor usage-summary/user-info async let flow with a cancellation-safe task-group implementation
• add regression coverage for the success/failure cases around the Cursor fetch path

Fixes #661.

[anirudhvee]

It looks like the failures are from the new urlSession: URLSession = .shared in CursorStatusProbe.swift. It probably just needs the usual #if canImport(FoundationNetworking) import there for Linux.

[hhh2210]

when can we publish a release for that?

[ratulsarna]

@hhh2210 Over the weekend