Add configurable media-aware managed session reaping

docs/protocol.md

@@ -305,6 +305,10 @@ message TextMessage {
   laptop sleep) that never produce a TCP EOF are cleaned up, and peers' audio engines
   `remove_stream` and stop PLC. The timeout and sweep interval are configurable via
   `server::Config::reaper_timeout_ms` / `reaper_sweep_ms` (set to 0 to disable).
+  The managed server uses `VoiceServerOptions.IdleTimeout` / `ReaperInterval` with the
+  same 45-second / 15-second defaults (zero idle timeout disables reaping). It refreshes
+  activity on parsed control envelopes, authenticated owned-stream voice, and exact
+  bound-endpoint keepalives; rejected media does not refresh activity. Timing is monotonic.
 - **UDP:** a separate lightweight keepalive on the media channel (voice.md §6) keeps NAT
   bindings alive and detects media-path failure independently of the control channel.
 - **Graceful disconnect.** A client ending its session sends `Disconnect { code = 0;