Add poker:leave on unmount and poker:kick to remove ghost participants

Frontend now emits poker:leave when PokerRoom unmounts, preventing
ghost participants. Also adds poker:kick socket event so any session
participant can remove a stale user — shows a small X button next to
each participant. Fixes deadlocked sessions where a disconnected user
blocks reveal (votes.size can never equal participants.size).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/src/index.js

@@ -343,6 +343,28 @@ io.on('connection', (socket) => {
     }
   });
 
+  throttled('poker:kick', async ({ sessionId, userKey }) => {
+    try {
+      if (!sessionId || !userKey) {
+        socket.emit('poker:error', { error: 'sessionId and userKey are required.' });
+        return;
+      }
+      if (!await canAccessSession(sessionId, socket.user.jiraCloudId)) {
+        socket.emit('poker:error', { error: 'Session not found.' });
+        return;
+      }
+      await leaveSession({
+        sessionId,
+        tenantCloudId: socket.user.jiraCloudId,
+        userKey
+      });
+      await emitSessionState(sessionId, socket.user.jiraCloudId);
+    } catch (error) {
+      console.error('[socket] poker:kick failed:', error);
+      socket.emit('poker:error', { error: safeError(error) });
+    }
+  });
+
   throttled('poker:leave', async ({ sessionId }) => {
     try {
       if (!sessionId) return;

frontend/src/components/PokerRoom.jsx

@@ -80,6 +80,7 @@ export default function PokerRoom({ session, issue, user, onSaved }) {
     }
 
     return () => {
+      socket.emit('poker:leave', { sessionId: session.id });
       socket.off('poker:participants', onParticipants);
       socket.off('poker:vote-update', onVoteUpdate);
       socket.off('poker:revealed', onRevealed);
@@ -98,6 +99,10 @@ export default function PokerRoom({ session, issue, user, onSaved }) {
     });
   }
 
+  function handleKick(userKey) {
+    socket.emit('poker:kick', { sessionId: session.id, userKey });
+  }
+
   function handleSave() {
     const estimate = Number(manualEstimate || suggestedEstimate);
     if (!Number.isFinite(estimate)) {
@@ -229,13 +234,24 @@ export default function PokerRoom({ session, issue, user, onSaved }) {
                       {isCurrentUser && <span className="text-slate-400"> (you)</span>}
                     </span>
                   </div>
-                  <div className="text-sm shrink-0 ml-2">
-                    {revealed && vote !== null && vote !== undefined ? (
-                      <span className="font-semibold text-purple-600 dark:text-purple-400">{vote}</span>
-                    ) : hasVoted ? (
-                      <span className="text-green-600 dark:text-green-400">✓</span>
-                    ) : (
-                      <span className="text-slate-400">...</span>
+                  <div className="flex items-center gap-2 shrink-0 ml-2">
+                    <span className="text-sm">
+                      {revealed && vote !== null && vote !== undefined ? (
+                        <span className="font-semibold text-purple-600 dark:text-purple-400">{vote}</span>
+                      ) : hasVoted ? (
+                        <span className="text-green-600 dark:text-green-400">✓</span>
+                      ) : (
+                        <span className="text-slate-400">...</span>
+                      )}
+                    </span>
+                    {!isCurrentUser && (
+                      <button
+                        onClick={() => handleKick(participant.userKey)}
+                        className="text-slate-400 hover:text-red-500 dark:hover:text-red-400 text-xs cursor-pointer bg-transparent border-none p-0"
+                        title="Remove participant"
+                      >
+                        ✕
+                      </button>
                     )}
                   </div>
                 </div>