Fix bonus answer box opening for all players in multiplayer

[Copilot]

When bonuses are enabled in multiplayer, clicking "Reveal" to start the bonus answer phase showed the answer input box to all connected players instead of only those on the eligible team.

Root Cause

BonusClient.startBonusAnswer unconditionally removes d-none from the answer input group. The multiplayer client had no override to restrict this to eligible players.

Fix

Override startBonusAnswer in MultiplayerTossupBonusClient to hide the answer box for players not on the bonus-eligible team:

startBonusAnswer (data) {
  super.startBonusAnswer(data);
  const myTeamId = this.room.players[this.USER_ID]?.teamId;
  if (myTeamId !== undefined && myTeamId !== this.room.bonusEligibleTeamId) {
    document.getElementById('answer-input-group').classList.add('d-none');
  }
}

This mirrors the existing pattern used for tossup buzzes, where the answer box is already gated behind userId === this.USER_ID.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>answer box opens for all players when bonuses are enabled in multiplayer</issue_title>
<issue_description></issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes answer box opens for all players when bonuses are enabled in multiplayer #443

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.