Persist input type when erased and recreated in dataset evals

Erased and recreated inputs persist values but not types.

Reproduction:

1. Create an input {{somevar}}.
2. Change its type from path to string.
3. Set the string value to foo.
4. Erase {{somevar}} from the prompt, causing the input field to disappear, then retype it so the field reappears.

The recreated input is empty with type path (the default). Changing the type to string makes foo appear automatically: the value persisted, but the type did not.