The API lifespan unconditionally spawned log_collector_worker,
appending every container line to DECNET_INGEST_LOG_FILE. On hosts
that also run decnet-collector.service (installed by 'decnet init')
that's two tailers writing the same events to the same file — the
ingester then inserts each event twice and the dashboard shows every
command duplicated.
Add DECNET_EMBED_COLLECTOR (default false), matching the existing
DECNET_EMBED_PROFILER and DECNET_EMBED_SNIFFER pattern directly
above this block. Single-process dev setups without systemd can flip
it on to restore the all-in-one behaviour; multi-process production
gets the single-writer invariant by default.