Randomization with seed error: number cannot be converted to BigInt, it's not an integer

[latin-panda]

Web Forms version and package (e.g. are you using web-forms or only the engine?)

Web Forms v0.5.0, main branch at 4b31432

Browser and version

Chrome v131.0.6778.265

Device used

MacOs - Desktop

Problem description

The following error pops up when refreshing a freshly uploaded form with a seed defined like this once(substr(decimal-date-time(now()), 8)).

Steps to reproduce the problem

• Upload a form that uses the randomization feature with a seed. For example:
  sample form
• Click preview
• See how form loads without error
• Reload the browser a couple of times
• See popup with error

Video:
https://github.com/user-attachments/assets/92848dc5-3b6d-4528-aaad-79daf1508ef7

Expected behavior

It should not throw an error when reloading the form, and the randomization should work with a seed like once(substr(decimal-date-time(now()), 8)).

Other information

• I see this issue in the Web Form preview and when running the project locally
• The same form works fine in the Enketo implementation: https://getodk.org/xlsform/
• This form uses the Rank widget, which has yet to be implemented, but the XPath random and seed have already been implemented.

[latin-panda]

Today, I tried the solution in this PR. I pulled, reinstalled, rebuilt, and ran the project, but the error still appears on reload.