[Victor Hugo Macedo Paes Leme (zerotohero3)]

Summary

• fastForward() truncated ticks with | 0, so anything over 2^31 - 1 ms (~24.8 days) wrapped around: 25 days threw "Cannot fast-forward to the past", 50 days only moved ~7h. Use Math.trunc() instead, same result for smaller values.
• | 0 was also what turned NaN/Infinity into a no-op on the current page (they still broke Date after a reload, since the init-script log keeps the raw value), and without it fastForward(Infinity) spins forever on any interval. Reject non-finite ticks in parseTicks(), like parseTime() already does for invalid dates. That covers runFor(NaN) too, which used to leave Date.now() as NaN.

Fixes #43783

[Victor Hugo Macedo Paes Leme (zerotohero3)]

@microsoft-github-policy-service agree