Changelog
- Add section 50 to reverse_engineered.md: CDlgTrade grid owner IDs, trade data
structure at hero+0x1920, CMsgTrade action dispatch table, MsgItemInfo action 7
partner-view remove mechanism, trade grid UID-vs-index gotcha
- Update Trade.md with removing items section covering packet flow and dual-packet
design (ReturnItem to owner, TradeRemove to partner)