fix: normalize Temporal objects to prevent native/polyfill mixing

[KristjanESPERANTO]

The Problem

Starting with V8 14.4 (Electron 40, Chrome 134), JavaScript environments include native Temporal API support. Prior versions like V8 14.2 (Electron 39) do not have native Temporal.

When external libraries pass native Temporal objects to rrule-temporal, which internally uses the polyfill, operations like until() and compare() fail with errors:

TypeError: Temporal error: Must specify time zone.

This happens because the two Temporal implementations have different constructors, and methods like ZonedDateTime.until() reject objects from a different implementation.

In practice, this breaks applications using libraries like node-ical in Electron 40, where recurring calendar events fail to expand.

The Solution

Before calling until() or compare(), we now normalize all Temporal objects to the polyfill implementation by converting them through ISO strings:

const normalized = Temporal.ZonedDateTime.from(original.toString());

This ensures both operands use the same Temporal implementation, avoiding the type mismatch.

Testing

Added 7 regression tests covering the affected code paths in between().

Note: The tests use only polyfill objects and cannot reproduce the actual native/polyfill mixing scenario. The fix was validated in production environments with native Temporal API.

[ggaabe]

@KristjanESPERANTO rrule-temporal 2.0 will likely be a modified Bring-Your-Own-Temporal version where it doesn't include Temporal, and it accepts a Temporal interface where the developer passes in whichever Temporal they're using

[KristjanESPERANTO]

Sounds good! And thanks for the merge 🙂