Polyfill: Check that time is not start-of-day in ToTemporalInstant

[catamorphism]

The TemporalInstantString production requires a Time, so time will never be start-of-day in this code.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.76%. Comparing base (03f9057) to head (efec08a).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3230   +/-   ##
=======================================
  Coverage   96.75%   96.76%           
=======================================
  Files          22       22           
  Lines       10398    10392    -6     
  Branches     1859     1858    -1     
=======================================
- Hits        10061    10056    -5     
  Misses        289      289           
+ Partials       48       47    -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.