Long-lived process that owns the :conduit_mcp_sessions ETS table so the table outlives short-lived request handlers.

Started under ConduitMcp.Supervisor by ConduitMcp.Application. This is the same pattern used by ConduitMcp.Tasks.EtsStore.Owner, ConduitMcp.Cancellation.Owner, ConduitMcp.Transport.SSE.Owner, ConduitMcp.Transport.SSEStream.Owner and ConduitMcp.OAuth.KeyProvider.JWKS.Owner.

The ConduitMcp.EtsOwner process deliberately holds no state and answers no calls — reads and writes go directly to the :public table from the calling process. Do not turn it into a handle_call gateway.