There’s a lot of duplication here that’s probably worth extracting
despite not meeting the three-repetitions rule because we were
already simulating the API being for a task by including the task
name in the URL.

This is a barely-different copypaste from the task fs acceptance
tests… I’m not sure what’s the best way to accomplish this!

The assumption that we should strip the task name path prefix
is no longer correct if we want to be able to browse the
allocation without a task. This changes the task filesystem
acceptance test files to all be nested within a task name
directory, which mirrors how it works in the real setup.

The interface here is still subpar, with the expectations of
the various things dangling off `this.` (files? directory?),
but maybe some cleanup is possible…

There’s one left that has some duplication but it doesn’t
seem worth extracting due to how much customisation it
would require.

Another combination could happen if I extract something like
an fs-link component 🤔

This contains some of the duplication scattered about where
filesystem links are slightly different in two dimensions.

There’s no need to have these calculations scattered everywhere.

It makes more sense to concentrate these functions in the
allocation adapter.

I’d LOVE for some Prettier-esque approach to this 😝