Fix join/leave messages appearing at wrong turn in battle log

[surfnWOB]

In the Preact client, spectators and players joining a battle would appear grouped together at the current turn instead of at their correct historical positions in the battle log.

Changes:

1. BattleRoom.receiveLine (new override in panel-battle.tsx):

• Handles user list updates for join/leave/name
• Routes messages to battle (if exists) or backlog (for later processing by BattlePanel)
• Keeps ChatRoom clean with no battle-specific conditionals

2. Battle.runMajor (simplified in battle.ts):

• Join/leave/name handlers now just log the message
• User list management delegated to BattleRoom

Testing:

• Spectate a live battle or watch a replay
• Join messages should appear at their correct historical positions