Set expeditedFlagged on Determination create in eligibility state machine

[arpitjain099]

The intake.application.submitted handler creates a Determination without expeditedFlagged, but the resolved schema marks that field required and non-nullable and the mock-server engine leaves required non-nullable scalars to the caller, so generated Zod clients reject every list/get Determination response with expected boolean, received undefined (issue #359). This adds expeditedFlagged: false to the create body, which matches the field description (set at submission, then the existing flag-expedited action promotes it to true once expedited screening criteria are met).

I also added a small regression test that asserts the Determination create body supplies every required writable field of the schema; it fails on the old code and passes with the fix, and the existing state-machine unit tests still pass. I left the Interview appointments second site from the issue comment out of this PR since it lives in intake-state-machine.yaml and the reporter noted it may be a separate engine default, so happy to follow up on that separately if you'd like it here too.

[mryhmln]

Thanks for the fix — the approach is correct and the regression test is a nice addition.

Two small things before we merge:

1. Could you rebase on main so CI can run the full test suite?
2. Since the Interview appointments piece from state-machine: Determination create omits required expeditedFlagged; Zod rejects every list/get response #359 is out of scope here, would you mind updating the PR description to say "Partially addresses state-machine: Determination create omits required expeditedFlagged; Zod rejects every list/get response #359" so the issue stays open for the follow-up?