feat(lib): per-member room statistics from the JoinRoom reply

The JoinRoom (code 14) reply carries, after the membership list, four
parallel vectors describing each member: status, share statistics, free
upload slots and country. The handler stopped after the usernames, so all of
it was discarded. It is now parsed and exposed as Client::room_member_stats.

Issue #48 asked for RoomStats (57) and RoomListStats (55). Those codes are
UserInterests and MyRecommendations in the Soulseek protocol; there is no
RoomStats message on the wire. Per-room user counts already arrive with
RoomList (64), which the client handles, and the per-member statistics are
part of the JoinRoom reply -- so that is where this adds them.

- join_room.rs: parse the stat vectors, each bounded by the payload so a
  hostile count cannot hang or overallocate
- types::RoomUserStats; every field looked up positionally so a server
  sending short vectors (or omitting countries) does not shift the roster
- ServerMessage/ClientOperation::RoomMemberStats and the context snapshot
  behind Client::room_member_stats, replaced on each rejoin

soulseek-rs-lib/src/client/mod.rs

@@ -5,7 +5,8 @@ use crate::actor::server_actor::{
 use crate::download_store::{DownloadStore, collect_failed_tokens};
 use crate::types::{
     ClientVersion, DownloadMetadata, DownloadStatus, RoomEvent, RoomInfo,
-    SessionLoss, SessionWatch, UserInfo, UserPresence, UserStats, UserStatus,
+    RoomUserStats, SessionLoss, SessionWatch, UserInfo, UserPresence,
+    UserStats, UserStatus,
 };
 use crate::utils::logger;
 use crate::{
@@ -278,6 +279,11 @@ pub enum ClientOperation {
     /// Something happened in the chat-room subsystem (list refreshed, a room
     /// joined/left, a message said, a member joined/left).
     RoomEvent(RoomEvent),
+    /// Per-member statistics from a `JoinRoom` reply.
+    RoomMemberStats {
+        room: String,
+        stats: Vec<RoomUserStats>,
+    },
     /// The server announced how many seconds must pass between wishlist
     /// searches.
     WishlistInterval(u32),
@@ -325,6 +331,9 @@ pub struct ClientContext {
     /// Who is in each room we have joined, kept current from the membership
     /// the server sends on join plus the later join/leave events.
     room_members: HashMap<String, Vec<String>>,
+    /// Per-member statistics for each joined room, from the stat vectors the
+    /// server sends alongside the membership list.
+    room_member_stats: HashMap<String, Vec<RoomUserStats>>,
     /// What the server has told us about other users, merged across the
     /// separate status and statistics replies.
     user_info: HashMap<String, UserInfo>,
@@ -415,6 +424,7 @@ impl ClientContext {
             room_list: Vec::new(),
             room_events: Vec::new(),
             room_members: HashMap::new(),
+            room_member_stats: HashMap::new(),
             user_info: HashMap::new(),
             wishlist_interval: None,
             privileged_users: HashSet::new(),
@@ -515,6 +525,29 @@ impl ClientContext {
         self.room_members.get(room).cloned().unwrap_or_default()
     }
 
+    /// Record the per-member statistics of a room we just joined, replacing
+    /// any previous snapshot for it.
+    pub fn apply_room_member_stats(
+        &mut self,
+        room: String,
+        stats: Vec<RoomUserStats>,
+    ) {
+        self.room_member_stats.insert(room, stats);
+    }
+
+    /// What the server reported about the members of `room`, sorted by name,
+    /// or empty for a room we have not joined.
+    #[must_use]
+    pub fn room_member_stats(&self, room: &str) -> Vec<RoomUserStats> {
+        let mut stats = self
+            .room_member_stats
+            .get(room)
+            .cloned()
+            .unwrap_or_default();
+        stats.sort_by(|a, b| a.username.cmp(&b.username));
+        stats
+    }
+
     /// The latest snapshot of the public chat-room list.
     #[must_use]
     pub fn room_list(&self) -> Vec<RoomInfo> {