fix(room): align ReactionGroup types with frontend and guard reaction update handler

- Fix ReactionGroup.count: i64 -> i32 and users: Vec<Uuid> -> Vec<String>
  to match frontend ReactionItem (count: number, users: string[]).
  Mismatched types caused the WS reaction update to silently fail.
  Also update ReactionItem in api/ws_types.rs to match.
- Add activeRoomIdRef guard in onRoomReactionUpdated to prevent stale
  room state from processing outdated events after room switch.
- Switch from prev.map() to targeted findIndex+spread in onRoomReactionUpdated
  to avoid unnecessary array recreation.

libs/api/room/ws_types.rs

@@ -449,9 +449,9 @@ impl From<room::MessageReactionsResponse> for ReactionListData {
 #[derive(Debug, Clone, Serialize)]
 pub struct ReactionItem {
     pub emoji: String,
-    pub count: i64,
+    pub count: i32,
     pub reacted_by_me: bool,
-    pub users: Vec<Uuid>,
+    pub users: Vec<String>,
 }
 
 #[derive(Debug, Clone, Serialize)]

libs/queue/types.rs

@@ -40,9 +40,10 @@ pub struct RoomMessageEvent {
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct ReactionGroup {
     pub emoji: String,
-    pub count: i64,
+    pub count: i32,
     pub reacted_by_me: bool,
-    pub users: Vec<Uuid>,
+    /// Stored as strings (UUIDs) to match the frontend's `users: string[]` type.
+    pub users: Vec<String>,
 }
 
 impl From<RoomMessageEnvelope> for RoomMessageEvent {

libs/room/src/reaction.rs

@@ -11,9 +11,9 @@ use uuid::Uuid;
 #[derive(Debug, Clone, serde::Serialize, utoipa::ToSchema)]
 pub struct ReactionGroupResponse {
     pub emoji: String,
-    pub count: i64,
+    pub count: i32,
     pub reacted_by_me: bool,
-    pub users: Vec<Uuid>,
+    pub users: Vec<String>,
 }
 
 #[derive(Debug, Clone, serde::Serialize, utoipa::ToSchema)]
@@ -83,9 +83,9 @@ impl RoomService {
             .into_iter()
             .map(|g| ReactionGroup {
                 emoji: g.emoji,
-                count: g.count,
+                count: g.count as i32,
                 reacted_by_me: g.reacted_by_me,
-                users: g.users,
+                users: g.users.into_iter().map(|u| u.to_string()).collect(),
             })
             .collect();
         self.queue
@@ -121,9 +121,9 @@ impl RoomService {
             .into_iter()
             .map(|g| ReactionGroup {
                 emoji: g.emoji,
-                count: g.count,
+                count: g.count as i32,
                 reacted_by_me: g.reacted_by_me,
-                users: g.users,
+                users: g.users.into_iter().map(|u| u.to_string()).collect(),
             })
             .collect();
         self.queue
@@ -258,11 +258,15 @@ impl RoomService {
         grouped
             .into_iter()
             .map(|(emoji, user_reactions)| {
-                let count = user_reactions.len() as i64;
+                let count = user_reactions.len() as i32;
                 let reacted_by_me = current_user_id
                     .map(|uid| user_reactions.iter().any(|r| r.user == uid))
                     .unwrap_or(false);
-                let users = user_reactions.iter().take(3).map(|r| r.user).collect();
+                let users = user_reactions
+                    .iter()
+                    .take(3)
+                    .map(|r| r.user.to_string())
+                    .collect();
 
                 ReactionGroupResponse {
                     emoji,

src/contexts/room-context.tsx

@@ -517,15 +517,18 @@ export function RoomProvider({
           }
         },
         onRoomReactionUpdated: (payload: RoomReactionUpdatedPayload) => {
+          // Guard: ignore events for rooms that are no longer active.
+          // Without this, a WS event arriving after room switch could update
+          // the wrong room's message list (same message ID, different room).
+          if (!activeRoomIdRef.current) return;
+
           setMessages((prev) => {
-            const updated = prev.map((m) =>
-              m.id === payload.message_id
-                ? { ...m, reactions: payload.reactions }
-                : m,
-            );
+            const existingIdx = prev.findIndex((m) => m.id === payload.message_id);
+            if (existingIdx === -1) return prev;
+            const updated = [...prev];
+            updated[existingIdx] = { ...updated[existingIdx], reactions: payload.reactions };
             // Persist reaction update to IndexedDB
-            const msg = updated.find((m) => m.id === payload.message_id);
-            if (msg) saveMessage(msg).catch(() => {});
+            saveMessage(updated[existingIdx]).catch(() => {});
             return updated;
           });
         },