[ty] Tweak how we show qualified auto-import completions
Specifically, we make two changes:
1. We only show `import ...` when there is an actual import edit.
2. We now show the text we will insert. This means that when we
insert a qualified symbol, the qualification will show in the
completions suggested.
Ref https://github.com/astral-sh/ty/issues/1274#issuecomment-3352233790
