Fix user input

[crutchcorn]

This PR builds on top of this PR: #401, please merge it first

This PR (specifically, this commit: 2f7ec1d) aims to fix user input from it's original broken state.

It includes tests to validate the fix.

However, I'm not a huge fan of this fix, as it duplicates the method of setting a value between the Form and Field. I'd much rather either:

• Add a listener to the form from the field that updates the field when the form is updated
• Abstract that away into a computed item in @tanstack/store that allows us to do this consistently with derived state

[tannerlinsley]

Happy to merge whatever you see fit. Just go for it Corbin!