fix(effect): stop Schedule.cron crashing on a non-finite clock

[eldardada]

Resolves #6292.

Problem

Advancing the clock past the end of time, e.g. TestClock.adjust(Infinity), crashes a running Schedule.cron with an uncaught IllegalArgumentException: Invalid date that kills the fiber:

IllegalArgumentException: Invalid date
  at unsafeFromDate (internal/dateTime.ts)
  at unsafeMakeZoned (internal/dateTime.ts)
  at match (Cron.ts)
  at ScheduleImpl.step (internal/schedule.ts)

Cause

The cron schedule step turns the current time into a Date and runs calendar math on it:

const date = new Date(now)
if (initial && Cron.match(cron, date)) { ... }
next = Cron.next(cron, date).getTime()

When now is non-finite, new Date(now) is an Invalid Date. Cron.match / Cron.next then call dateTime.unsafeMakeZoned, whose date.getTime() is NaN, and unsafeFromDate throws by design. So the real bug is that Schedule.cron hands an invalid instant to the cron helpers.

Time-based neighbours like Schedule.fixed and Schedule.spaced do not crash here: they work with plain now + delay arithmetic and never build a Date, so a non-finite now just flows through.

Fix

Guard the cron step: when now is non-finite there is no instant to match, so finish the schedule (ScheduleDecision.done) instead of throwing. This brings cron in line with how the other time-based schedules behave when the clock runs past the end of time, and leaves all finite behaviour untouched.

Verification

Reproduced the crash deterministically (cron fails while fixed / spaced succeed under the same now = Infinity), confirmed the fix turns the failure into a clean Success, and added a regression test in the cron suite. pnpm check (tsc), eslint, and the full Schedule test suite (83 tests) all pass. Changeset included (effect: patch).

[changeset-bot]

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Latest commit: 63211d3

The changes in this PR will be included in the next version bump.

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