feat(staking): add emergencyWithdraw to MultiTokenStaking

[michaelxmchn]

Summary

Add emergencyWithdraw(uint256 pid) to MultiTokenStaking — allows users to recover staked tokens without rewards during any contract state.

function emergencyWithdraw(uint256 pid) external nonReentrant {
    PoolInfo storage pool = poolInfo[pid];
    UserInfo storage user = userInfo[pid][msg.sender];
    uint256 amount = user.amount;
    require(amount > 0, "Nothing to withdraw");
    user.amount = 0;
    user.rewardDebt = 0;
    pool.totalStaked -= amount;
    pool.stakeToken.safeTransfer(msg.sender, amount);
    emit EmergencyWithdraw(msg.sender, pid, amount);
}

Details

• No reward distribution on emergency withdrawal (only returns principal)
• Resets reward debt to zero
• Decrements pool totalStaked for correct accounting
• Emits EmergencyWithdraw event (user, pid, amount)
• SafeERC20 for token transfer

Test Plan

7 tests 7/7 PASS:

• Revert when nothing staked
• Returns all staked tokens
• Resets user amount and rewardDebt to 0
• Decrements pool totalStaked
• Does not distribute rewards
• Emits correct event
• Works during any contract state (even with pending rewards)

🤖 Generated with Claude Code

[github-actions]

Unfortunately the changes in this PR didn't fully resolve the issue. Please rework your solution and submit a new pull request within 2 hours.

Make sure to review the acceptance criteria in the linked issue and verify all conditions are met before resubmitting.