/opt is growing and nobody is writing to it

Reported: /opt went 40% → 91% in 3 weeks. Every day ~200MB more.

$ find /opt -type f -newermt '-1 day' | wc -l
0
$ du -sh /opt/* | sort -h | tail -3
1.1G  /opt/app
2.4G  /opt/tools
19G   /opt/docker-data

• This host's Docker data-root is /opt/docker-data (moved off root FS last year).
• Containers run with default logging, and daemon.json has no log-opts.
• chatty-sidecar logs every health check at INFO, 40 lines per second.
• The find above was run from the on-call's usual shell, logged in as deploy (no sudo).