fix(harness): make orphan sweep timeout boundary inclusive (#2619)

## Description

### Background

The Windows CI failure was caused by a time-boundary race in orphan-task
sweeping.
`writeTaskRecord()` refreshes `lastUpdatedAt`; with `Duration.ZERO`, the
record
can have the same timestamp as the sweep threshold. The previous strict
comparison left that record in `RUNNING`.

### Changes

- Treat task records at the orphan-timeout boundary as stale.
- Allow the sweeper’s reference time to be supplied for deterministic
testing.
- Update the regression test to use the persisted timestamp as the exact
  zero-timeout boundary.

### Impact

This prevents platform clock-resolution differences from causing stale
background tasks to remain `RUNNING`, eliminating the observed Windows
CI flake.