Choose which channels this workspace ingests (CLO-387).

Owner-only, unlike the member-visible read above: deciding what enters the knowledge graph — and therefore what every workspace member can query — is not a browsing action.

Newly selected channels are backfilled immediately, since selecting a channel is the moment the owner asked for its history. De-selecting only stops future ingestion; already-ingested content stays searchable (deleting from a knowledge graph is destructive and entities may be referenced elsewhere — see CLO-391).