fix(room-info): hide Leave Room button when user is alone

Hide the "Leave Room" button when the user is the only member in the
room. Leaving when you're alone doesn't make conceptual sense - it
would just auto-create another empty room.

The button now only appears when roomData.members.length > 1.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

apps/web/src/components/nav/RoomInfo.tsx

@@ -673,8 +673,8 @@ export function RoomInfo({
                     <span>Join Another</span>
                   </DropdownMenu.Item>
 
-                  {/* Leave Room - only show when in a room */}
-                  {roomId && (
+                  {/* Leave Room - only show when in a room with other members */}
+                  {roomId && roomData && roomData.members.length > 1 && (
                     <>
                       <DropdownMenu.Separator
                         style={{