Shared container storage and server-tracked dropped items

[gherman7755]

Problem

Two long-standing issues when playing together:

1. Items stored in containers disappear. Container contents only lived on the server while someone was in the cell. Once everyone left, the entities were destroyed, and the next player to enter registered their own local copy as the truth. Items a guest stored were wiped as soon as the host (or anyone without them) entered first, and player home chests could not be shared at all.
2. Dropped items are not visible to other players. Drop sync existed behind bEnableItemDrops but was off by default because each client created an unrelated copy, so a dropped item could be picked up once per player.

Changes

Containers (first commit)

• Container entities are kept for the whole server session; only doors are still dropped when a cell empties.
• Player home (NoResetZone) chests merge each player's local contents into the server state the first time that player sees them (Inventory::MergeMissing), and players already in the cell receive the added entries. bSyncPlayerHomes now defaults to true.
• Server container inventories never store negative entries (AddOrRemoveEntryClamped).
• Client object entities are deduplicated by form id and cleared on disconnect, so container inventory changes are no longer sent with a stale server id.

Dropped items (second commit)

• New DroppedItemService on client and server, plus DropItemRequest/DropItemResponse, NotifyDroppedItems, NotifyDroppedItemRemoved, PickupDroppedItemRequest/PickupDroppedItemResponse.
• The dropping client waits until the item comes to rest and reports its cell and position. The server assigns an id, sends it to players in range, and to players entering that area later.
• Other clients place their copy at that position and map it to the server id (reusing a leftover local copy nearby, e.g. after reconnecting).
• Pickups are arbitrated by the server: the first request wins, every other copy is removed, and a player who lost the race has the item removed again.
• uMaxDroppedItems (default 1000) caps how many dropped items the server tracks. bEnableItemDrops now defaults to true.
• The old Drop relay through NotifyInventoryChanges is no longer used; the item simply leaves the dropper's inventory there.
• HookDropObject now passes an explicit location in front of local actors when the game provides none. Without it, single items dropped by the player sometimes landed near the world origin instead of in front of them.

Testing

• TPTests pass, including new round-trip tests for the messages and tests for the merge/clamp helpers.
• Tested in game with two players on Skyrim AE:
  • a guest stores items, leaves, and the host enters: items are still there;
  • shared chest in a player home: both players' items are kept;
  • single items and stacks dropped indoors and outdoors show up at the same spot for both players;
  • both players grabbing the same item: only one keeps it.

Notes / open points

• Server state is in-memory only. After a server restart, the first player to enter a non-home cell still defines its container contents.
• Containers outside player homes no longer respawn their loot while the server is running.
• Existing STServer.ini files keep their old values for bEnableItemDrops / bSyncPlayerHomes.

[miredirex]

Hi. I'm already working on item drops #913

Please write PR descriptions by hand instead of using ai, and discuss submitting such big changes with the team first in our discord

[miredirex]

Sorry, closing for the following reasons:

• overhauled item drops is already work-in-progress and is going to land in the upcoming ST update
• "first-time contributor" working on a big feature without prior discussion
• heavy AI use with no AI disclosure, plus an ai-written PR description

You're still welcome to contribute (and use AI too, we don't mind), just pick a small-scope task. We will soon have AGENTS.md that should help