docs/oasis-node/cli: Document compact command

Author: martintomazic

docs/oasis-node/cli.md

@@ -331,3 +331,28 @@ response:
 ```
 oasis1qqncl383h8458mr9cytatygctzwsx02n4c5f8ed7
 ```
+
+## storage
+
+### compact-experimental
+
+Run
+
+```sh
+oasis-node storage compact-experimental --config /path/to/config/file
+```
+
+to trigger manual compaction of consensus database instances:
+
+```sh
+{"caller":"storage.go:310","level":"info","module":"cmd/storage","msg":"Starting database compactions. This may take a while...","ts":"2025-10-08T09:18:22.185451554Z"}
+```
+
+If pruning was not enabled from the start or was recently increased, then even after successful pruning, the disk usage may stay the same.
+
+This is due to the LSM-tree storage design that BadgerDB uses. Concretely, deleting a key only marks it as ready to be deleted (a tombstone entry). The actual removal of the stale data happens later during the compaction.
+
+During normal operation, compaction happens in the background. However, BadgerDB
+is intentionally lazy, trading write throughput for disk space among other things. Therefore it is expected that in case of late pruning, the disk space may stay constant or not be reclaimed for a very long time.
+
+This command gives operators manual control to release disk space during maintenance periods.