docs: add CPackageMgr RE and depot grid owner ids to reverse_engineered

- Add section 30.8 documenting the CPackageMgr client-side manager class with subsections for methods (GetSingletonPtr, FindPackage, SendDeposit, SendWithdraw, SendListItems), CPackage object layout (this[9]/[10]/[12]), CDlgDepot/CDlgVipDepot field offsets for npcId/whType, the three drop-deposit drag-drop receiver handlers, and the CItem field-72 bit predicates

- Document the __thiscall calling-convention trap on CPackageMgr_SendDeposit (0x7E9D1D) and CPackageMgr_SendWithdraw (0x7E9DAF) — both auto-typed as __stdcall by IDA but the inner FindPackage relies on __EH_prolog3 preserving ECX

- Add the verified 6609 grid owner ID table to section 43.5 (DLG_MPCGOODS=12, DLG_DEPOT=16, DLG_VIPDEPOT=61)

- Extend section 43.6 (CHero::SellItem trap) with a note about the same trap being hit again on CPackageMgr methods, plus a heuristic for spotting it (retn 0Ch + IDA __stdcall + check the call site for mov ecx, ...)

- Update the index with the new 30.8.1 through 30.8.5 entries