[ty] Add a test capturing sub-optimal auto-import heuristic
Specifically, here, we'd probably like to add `TypedDict` to
the existing `from typing import ...` statement instead of
using the fully qualified `typing.TypedDict` form.
To test this, we add another snapshot mode for including imports
that a completion will insert when selected.
Ref https://github.com/astral-sh/ty/issues/1274#issuecomment-3352233790
