feat(daemon): publish room member statistics over RPC and the CLI

The statistics parsed from the JoinRoom reply were reachable only from the
library. They answer the question `room users` already exists to ask -- who
is in here, and are they worth downloading from -- so they belong on its
output rather than behind a second call.

- proto: room.member_stats, with a RoomUserStatsDto carrying status, share
  counts, free slots and country
- SessionApi::room_member_stats, so local and remote sessions stay
  interchangeable; the status word is decoded through one shared helper
  rather than a third copy of the match
- `room users` now emits status, average_speed, shared_files,
  shared_folders, slots_free and country, each null when the server said
  nothing, documented in SKILL.md
- docs/openrpc.json regenerated from the wire types

soulseek-rs/src/SKILL.md

@@ -140,7 +140,11 @@ cheapest way to prove the credentials and connection work.
 server did not answer — those are different facts, so do not treat null as 0.
 
 **`room list`** — `room`, `users`.
-**`room users <room>`** — `room`, `user`.
+**`room users <room>`** — `room`, `user`, `status`, `average_speed`,
+`shared_files`, `shared_folders`, `slots_free`, `country`. Everything but
+`room` and `user` is `null` when the server sent no statistics for that
+member — `null` means unknown, not zero. `slots_free` of 0 means the peer has
+no free upload slot right now, so a download from them will queue.
 **`room listen <room>`** — streams `type`, `room`, `user`, `message`.
 **`room say <room> <message>`** — prints nothing; exit 0 is the confirmation.