A segment that the platform already acknowledged could still be extended by
the next tailed line, so its checksum covered entries stored under a different
batch. The platform then rejected the same body every second while
RejectStreamAfter skipped it, because it only quarantined segments that start
after the platform latest. Every newly allocated line was quarantined by the
following recovery pass, so live log ingest never resumed.
Quarantine pending segments that reach beyond the acknowledged range, never
extend a segment the platform already stored, and log the gap recovery so a
stalled stream is diagnosable from the spool alone.