Describe the issue
The TS docs for cancellation show object destructuring at the top of the function.

This will not function correctly: JavaScript will resolve the getter at the top of the function into a primitive boolean, which cannot change during the task lifetime. If the task has cancelled === false when it starts, it will remain false for however long the function runs.

To read a dynamic value (i.e., for the getter to actually behave like a getter), it must be read like if (ctx.cancelled).

Additional context
It would also be nice if the docs indicated why both cancelled and abortController are offered.

Having abortController makes sense - we can pass it to fetch etc. But given could check if abortController.signal.aborted, it's not clear when ctx.cancelled` is appropriate to use.