feat(host): 대기실 실시간 참가자 목록 + 강퇴 기능

src/features/sessions/api/index.ts

@@ -49,3 +49,11 @@ export async function endSession(sessionId: string): Promise<EndSessionResponse>
   );
   return data;
 }
+
+/** 참가자 강퇴 (호스트) */
+export async function deleteParticipant(
+  sessionId: string,
+  participantId: string,
+): Promise<void> {
+  await apiClient.delete(`/sessions/${sessionId}/participants/${participantId}`);
+}

src/features/sessions/hooks/index.ts

@@ -3,3 +3,4 @@ export { useCreateSession } from './useCreateSession';
 export { useStartSession } from './useStartSession';
 export { useNextQuestion } from './useNextQuestion';
 export { useEndSession } from './useEndSession';
+export { useKickParticipant } from './useKickParticipant';

src/features/sessions/hooks/useKickParticipant.ts

@@ -0,0 +1,16 @@
+'use client';
+
+import { useMutation } from '@tanstack/react-query';
+import { deleteParticipant } from '../api';
+
+/**
+ * 참가자 강퇴 (호스트)
+ *
+ * 성공 시 서버가 /topic/.../participants 로 갱신된 목록을 브로드캐스트하므로
+ * 별도 invalidate 없이 소켓 이벤트로 목록이 갱신됩니다.
+ */
+export function useKickParticipant(sessionId: string) {
+  return useMutation({
+    mutationFn: (participantId: string) => deleteParticipant(sessionId, participantId),
+  });
+}

src/features/sessions/ui/HostWaitingClient.tsx

@@ -2,26 +2,26 @@
 
 import { useRouter } from 'next/navigation';
 import { useState } from 'react';
-import { useSession, useStartSession } from '../hooks';
+import { useSession, useStartSession, useKickParticipant } from '../hooks';
 import { useSessionSocket } from '../socket/hooks';
 import { getApiErrorMessage } from '@/shared/api/error';
 import { CountUp } from '@/shared/ui/CountUp';
+import type { SessionParticipantsEvent } from '@/shared/types/api';
 
 export function HostWaitingClient({ sessionId }: { sessionId: string }) {
   const router = useRouter();
   const { data: session, isLoading } = useSession(sessionId);
   const { mutate: startSession, isPending } = useStartSession();
+  const { mutate: kick, isPending: kicking } = useKickParticipant(sessionId);
   const [errorMsg, setErrorMsg] = useState('');
+  const [participants, setParticipants] = useState<SessionParticipantsEvent['participants']>([]);
 
-  // WebSocket — 참가자 입장 이벤트 수신
+  // WebSocket — 참가자 입·퇴장 실시간 목록
   const { connected } = useSessionSocket({
     sessionId,
     enabled: !!session,
-    onParticipants: () => {
-      // 참가자 목록 변경 시 session 쿼리 자동 refetch (3초 폴링)
-    },
+    onParticipants: (e) => setParticipants(e.participants),
     onStatus: (e) => {
-      // 세션 상태 변경 감지
       if (e.status === 'IN_PROGRESS') {
         router.push(`/host/sessions/${sessionId}/play`);
       }
@@ -52,7 +52,9 @@ export function HostWaitingClient({ sessionId }: { sessionId: string }) {
     );
   }
 
-  const canStart = !isPending && session.participantCount > 0;
+  // 실시간 인원: WS 목록이 있으면 그 길이, 없으면 폴링 카운트
+  const liveCount = participants.length > 0 ? participants.length : session.participantCount;
+  const canStart = !isPending && liveCount > 0;
 
   return (
     <div className="stage flex-1 min-h-screen flex flex-col items-center justify-center gap-8 p-8">
@@ -66,7 +68,7 @@ export function HostWaitingClient({ sessionId }: { sessionId: string }) {
         </h1>
       </div>
 
-      {/* PIN 디스플레이 — RED 네온 */}
+      {/* PIN — RED 네온 */}
       <div
         className="text-center"
         style={{ background: 'var(--color-primary)', boxShadow: 'var(--glow-red-neon)', borderRadius: 24, padding: '32px 56px' }}
@@ -86,7 +88,7 @@ export function HostWaitingClient({ sessionId }: { sessionId: string }) {
           style={{ background: connected ? 'var(--color-correct)' : 'var(--stage-muted)' }}
         />
         <span className="text-xl font-bold tabular" style={{ color: 'var(--stage-text)' }}>
-          <CountUp value={session.participantCount} />
+          <CountUp value={liveCount} />
         </span>
         <span className="text-xl font-bold" style={{ color: 'var(--stage-text)' }}>
           명 참가 중
@@ -98,6 +100,37 @@ export function HostWaitingClient({ sessionId }: { sessionId: string }) {
         )}
       </div>
 
+      {/* 참가자 목록 + 강퇴 */}
+      {participants.length > 0 && (
+        <div className="stage-card w-full max-w-md p-4 flex flex-col gap-2">
+          <p className="text-sm font-semibold" style={{ color: 'var(--stage-text)' }}>
+            참가자 목록
+          </p>
+          <div className="flex flex-col gap-1 overflow-y-auto" style={{ maxHeight: 240 }}>
+            {participants.map((p) => (
+              <div
+                key={p.participantId}
+                className="flex items-center justify-between px-3 py-2 rounded-xl"
+                style={{ background: 'rgba(255,255,255,0.05)' }}
+              >
+                <span className="text-sm truncate" style={{ color: 'var(--stage-text)' }}>
+                  {p.nickname}
+                </span>
+                <button
+                  type="button"
+                  onClick={() => kick(p.participantId)}
+                  disabled={kicking}
+                  className="text-xs font-semibold shrink-0 ml-2 hover:opacity-70 transition-opacity"
+                  style={{ color: 'var(--color-primary-disabled)', cursor: kicking ? 'not-allowed' : 'pointer' }}
+                >
+                  강퇴
+                </button>
+              </div>
+            ))}
+          </div>
+        </div>
+      )}
+
       {/* 세션 정보 */}
       <div className="flex gap-4 text-center">
         <div className="stage-card px-5 py-3">
@@ -130,7 +163,7 @@ export function HostWaitingClient({ sessionId }: { sessionId: string }) {
         {isPending ? '시작 중…' : '퀴즈 시작!'}
       </button>
 
-      {session.participantCount === 0 && (
+      {liveCount === 0 && (
         <p style={{ fontSize: 13, color: 'var(--stage-muted)' }}>
           참가자가 1명 이상 있어야 시작할 수 있습니다.
         </p>