setActiveReporterForTest function
Test-only seam: install a reporter as the active chokepoint target without
running the whole appInitErrorHandling branch, so _recordErrorSafe's
attached-vs-buffering split can be exercised in isolation. Pass null to
simulate the pre-attach (unattached) state.
Implementation
@visibleForTesting
void setActiveReporterForTest(ErrorReporter? reporter) {
_activeReporter = reporter;
}