Thanks for the reviews over the last few rounds, this has shaped up quite well.
That specific capability "don't inherit" was something that came up in a few contexts and is definitely something we can do in the future.
With the property wrapper approach it may be a bit weird how to express this, we may need a new wrapper? Because the goal with @TaskLocal would be to cause compile time Sendable-check failures once we're ready to enable them across the board, so it'd be hard to not do that check for @TaskLocal(inherit: .never), but it's something we could do in some way for sure.