feat(items): Phase F.2 ItemRepository + AppraiseRequest round-trip

Implements the item-state mirror + appraise round-trip infrastructure
on top of Phase F.1's GameEvent dispatcher.

Core layer (AcDream.Core/Items):
- ItemRepository: ConcurrentDictionary-backed live item state keyed by
  server ObjectId. Events: ItemAdded, ItemMoved, ItemRemoved,
  ItemPropertiesUpdated. MoveItem handles container / slot / equip
  location updates atomically and fires ItemMoved with old+new container
  ids. UpdateProperties merges a PropertyBundle patch (for appraise
  results) without clobbering existing untouched keys.

Wire layer (AcDream.Core.Net/Messages):
- AppraiseRequest (0x00C8 C→S, inside 0xF7B1 GameAction envelope):
  Build(sequence, targetGuid) → 16-byte body ready for SendGameAction.
- GameEvents.ParseIdentifyResponseHeader for 0x00C9 S→C — extracts
  (guid, appraiseFlags, success). Full PropertyBundle deserialization
  (the 10-flag bitfield-indexed tables) is a future pass; header alone
  is enough to route into the repository + surface "appraise complete"
  to UI.
- GameEvents.ParseWieldObject (0x0023) — server-driven equip.
- GameEvents.ParsePutObjInContainer (0x0022) — server-driven inventory
  move (item, container, placement).

Tests (11 new):
- ItemRepository: add/update fires correct event, move updates fields,
  missing-id returns false, remove, properties merge, clear.
- Wire: AppraiseRequest byte-exact encoding, IdentifyResponse header
  round-trip, WieldObject round-trip, PutObjInContainer round-trip.

Build green, 532 tests pass (up from 521).

Phase F.2 unblocks the Paperdoll + Inventory UI panels and the
"appraise on right-click" UX. Next pieces: PropertyBundle full
deserializer (AppraiseInfo 10-flag bitfield), outbound move/drop/
pickup actions.

Ref: r06 §1 (ItemType), §2 (EquipMask), §5 (appraise wire), §7 (pack
depth rules).
Ref: ACE GameEventIdentifyObjectResponse.cs for AppraiseInfo format.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/AcDream.Core.Net/Messages/AppraiseRequest.cs

@@ -0,0 +1,42 @@
+using System.Buffers.Binary;
+
+namespace AcDream.Core.Net.Messages;
+
+/// <summary>
+/// Outbound <c>0x00C8 IdentifyObject / Appraise</c> GameAction.
+///
+/// <para>
+/// Wire shape (inside the <c>0xF7B1</c> envelope):
+/// <code>
+///   u32 0xF7B1                   // GameMessage opcode (GameAction envelope)
+///   u32 gameActionSequence       // client-tracked sequence
+///   u32 0x00C8                   // GameAction sub-opcode
+///   u32 targetGuid               // whose appraisal we're requesting
+/// </code>
+/// </para>
+///
+/// <para>
+/// Server replies with a <c>0xF7B0 / 0x00C9 IdentifyObjectResponse</c>
+/// containing the full <c>AppraiseInfo</c> property bundle. See
+/// <c>GameEvents.cs</c> for the matching parser (once wired).
+/// </para>
+/// </summary>
+public static class AppraiseRequest
+{
+    public const uint GameActionEnvelope = 0xF7B1u;
+    public const uint SubOpcode = 0x00C8u;
+
+    /// <summary>
+    /// Pack an AppraiseRequest body (with envelope) ready to be handed
+    /// to <c>WorldSession.SendGameAction</c>.
+    /// </summary>
+    public static byte[] Build(uint gameActionSequence, uint targetGuid)
+    {
+        byte[] body = new byte[16];
+        BinaryPrimitives.WriteUInt32LittleEndian(body,            GameActionEnvelope);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(4),  gameActionSequence);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(8),  SubOpcode);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(12), targetGuid);
+        return body;
+    }
+}

src/AcDream.Core.Net/Messages/GameEvents.cs

@@ -145,6 +145,60 @@ public static class GameEvents
         return BinaryPrimitives.ReadUInt32LittleEndian(payload);
     }
 
+    // ── Appraise / identify ─────────────────────────────────────────────────
+
+    /// <summary>0x00C9 IdentifyObjectResponse header.</summary>
+    public readonly record struct IdentifyResponseHeader(
+        uint Guid,
+        uint AppraiseFlags,
+        bool Success);
+
+    /// <summary>
+    /// Parse the header of an <c>IdentifyObjectResponse (0x00C9)</c>.
+    /// Full property-bundle deserialization (int / bool / float / string
+    /// tables per the AppraiseFlags bitfield) is a future pass; this
+    /// header alone is enough for the UI to display "Appraise complete
+    /// on target X" and to route into the repository.
+    /// </summary>
+    public static IdentifyResponseHeader? ParseIdentifyResponseHeader(ReadOnlySpan<byte> payload)
+    {
+        if (payload.Length < 12) return null;
+        uint guid    = BinaryPrimitives.ReadUInt32LittleEndian(payload);
+        uint flags   = BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(4));
+        uint success = BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(8));
+        return new IdentifyResponseHeader(guid, flags, success != 0);
+    }
+
+    /// <summary>0x0023 WieldObject: server-driven equip.</summary>
+    public readonly record struct WieldObject(
+        uint ItemGuid,
+        uint EquipLoc,
+        uint WielderGuid);
+
+    public static WieldObject? ParseWieldObject(ReadOnlySpan<byte> payload)
+    {
+        if (payload.Length < 12) return null;
+        return new WieldObject(
+            BinaryPrimitives.ReadUInt32LittleEndian(payload),
+            BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(4)),
+            BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(8)));
+    }
+
+    /// <summary>0x0022 InventoryPutObjInContainer: server puts item into container slot.</summary>
+    public readonly record struct InventoryPutObjInContainer(
+        uint ItemGuid,
+        uint ContainerGuid,
+        uint Placement);
+
+    public static InventoryPutObjInContainer? ParsePutObjInContainer(ReadOnlySpan<byte> payload)
+    {
+        if (payload.Length < 12) return null;
+        return new InventoryPutObjInContainer(
+            BinaryPrimitives.ReadUInt32LittleEndian(payload),
+            BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(4)),
+            BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(8)));
+    }
+
     // ── Shared string reader (matches LoginRequest.ReadString16L) ───────────
 
     private static string ReadString16L(ReadOnlySpan<byte> source, ref int pos)

src/AcDream.Core/Items/ItemRepository.cs

@@ -0,0 +1,168 @@
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+
+namespace AcDream.Core.Items;
+
+/// <summary>
+/// Live item-state mirror — the client-side view of every item the
+/// server has spawned for this session. Owns <see cref="ItemInstance"/>
+/// records, tracks which container holds each item, and fires events so
+/// UI panels (inventory, paperdoll, hotbars) can redraw on change.
+///
+/// <para>
+/// Retail semantics (r06):
+/// <list type="bullet">
+///   <item><description>
+///     Every item is a <see cref="ItemInstance"/> with a unique
+///     <c>ObjectId</c>. CreateObject seeds it when the server tells us
+///     the item exists (in our inventory, on the ground, in a
+///     vendor's list, etc).
+///   </description></item>
+///   <item><description>
+///     Moves happen via <see cref="GameEventType"/>-carrying messages:
+///     <c>WieldObject</c>, <c>InventoryPutObjInContainer</c>,
+///     <c>InventoryPutObjectIn3D</c>, <c>ViewContents</c>,
+///     <c>CloseGroundContainer</c>.
+///   </description></item>
+///   <item><description>
+///     <c>InventoryServerSaveFailed</c> reverts a speculative local
+///     state change (e.g. when a drag-drop was rejected server-side).
+///   </description></item>
+/// </list>
+/// </para>
+///
+/// <para>
+/// Thread safety: designed for single-threaded use from the render
+/// thread; the event delegates run synchronously on the caller's
+/// thread. A <see cref="ConcurrentDictionary{TKey,TValue}"/> backs the
+/// map so plugin code can look up items from any thread without
+/// corrupting state.
+/// </para>
+/// </summary>
+public sealed class ItemRepository
+{
+    private readonly ConcurrentDictionary<uint, ItemInstance> _items = new();
+    private readonly ConcurrentDictionary<uint, Container> _containers = new();
+
+    /// <summary>Fires when an item is first added to the session.</summary>
+    public event Action<ItemInstance>? ItemAdded;
+
+    /// <summary>
+    /// Fires when an item's container / slot changes (moved between
+    /// packs, equipped, unequipped, dropped on ground). Old and new
+    /// container ids are 0 if origin or destination is "world" / "nowhere".
+    /// </summary>
+    public event Action<ItemInstance, uint, uint>? ItemMoved;
+
+    /// <summary>Fires when an item is removed from the session.</summary>
+    public event Action<ItemInstance>? ItemRemoved;
+
+    /// <summary>Fires when an item's properties are updated (typically after Appraise).</summary>
+    public event Action<ItemInstance>? ItemPropertiesUpdated;
+
+    public int ItemCount => _items.Count;
+    public int ContainerCount => _containers.Count;
+
+    public IEnumerable<ItemInstance> Items => _items.Values;
+    public IEnumerable<Container> Containers => _containers.Values;
+
+    /// <summary>
+    /// Look up an item by its server-assigned <c>ObjectId</c>.
+    /// </summary>
+    public ItemInstance? GetItem(uint objectId) =>
+        _items.TryGetValue(objectId, out var item) ? item : null;
+
+    /// <summary>
+    /// Look up a container by object id, creating a lightweight stub if
+    /// the id doesn't match any known container (defensive — avoids losing
+    /// references when the server announces a move into a container it
+    /// hasn't described yet).
+    /// </summary>
+    public Container? GetContainer(uint objectId) =>
+        _containers.TryGetValue(objectId, out var c) ? c : null;
+
+    /// <summary>
+    /// Register / refresh an item in the repository. Called on
+    /// CreateObject for item-typed weenies and on IdentifyObjectResponse
+    /// to fill in detail properties.
+    /// </summary>
+    public void AddOrUpdate(ItemInstance item)
+    {
+        ArgumentNullException.ThrowIfNull(item);
+        bool existed = _items.ContainsKey(item.ObjectId);
+        _items[item.ObjectId] = item;
+        if (!existed) ItemAdded?.Invoke(item);
+        else ItemPropertiesUpdated?.Invoke(item);
+    }
+
+    /// <summary>
+    /// Register a container. Idempotent.
+    /// </summary>
+    public void AddContainer(Container container)
+    {
+        ArgumentNullException.ThrowIfNull(container);
+        _containers[container.ObjectId] = container;
+    }
+
+    /// <summary>
+    /// Handle a server-driven move — called from
+    /// InventoryPutObjInContainer (0x0022) and WieldObject (0x0023)
+    /// handlers. Updates ContainerId / ContainerSlot / CurrentlyEquippedLocation
+    /// and fires ItemMoved.
+    /// </summary>
+    public bool MoveItem(uint itemId, uint newContainerId, int newSlot = -1,
+        EquipMask newEquipLocation = EquipMask.None)
+    {
+        if (!_items.TryGetValue(itemId, out var item)) return false;
+
+        uint oldContainer = item.ContainerId;
+        item.ContainerId = newContainerId;
+        item.ContainerSlot = newSlot;
+        item.CurrentlyEquippedLocation = newEquipLocation;
+
+        ItemMoved?.Invoke(item, oldContainer, newContainerId);
+        return true;
+    }
+
+    /// <summary>
+    /// Handle a server-driven remove (destroyed item, dropped into 3D
+    /// space, stolen, etc).
+    /// </summary>
+    public bool Remove(uint itemId)
+    {
+        if (!_items.TryRemove(itemId, out var item)) return false;
+        ItemRemoved?.Invoke(item);
+        return true;
+    }
+
+    /// <summary>
+    /// Apply a <see cref="PropertyBundle"/> patch (e.g. from an
+    /// <c>IdentifyObjectResponse</c>) to an existing item. Individual
+    /// keys in the incoming bundle overwrite existing values; keys not
+    /// present are left untouched.
+    /// </summary>
+    public bool UpdateProperties(uint itemId, PropertyBundle incoming)
+    {
+        if (!_items.TryGetValue(itemId, out var item)) return false;
+        foreach (var kv in incoming.Ints)     item.Properties.Ints[kv.Key] = kv.Value;
+        foreach (var kv in incoming.Int64s)   item.Properties.Int64s[kv.Key] = kv.Value;
+        foreach (var kv in incoming.Bools)    item.Properties.Bools[kv.Key] = kv.Value;
+        foreach (var kv in incoming.Floats)   item.Properties.Floats[kv.Key] = kv.Value;
+        foreach (var kv in incoming.Strings)  item.Properties.Strings[kv.Key] = kv.Value;
+        foreach (var kv in incoming.DataIds)  item.Properties.DataIds[kv.Key] = kv.Value;
+        foreach (var kv in incoming.InstanceIds) item.Properties.InstanceIds[kv.Key] = kv.Value;
+        ItemPropertiesUpdated?.Invoke(item);
+        return true;
+    }
+
+    /// <summary>
+    /// Flush the repository — typically called on logoff or teleport
+    /// that drops the session's item state.
+    /// </summary>
+    public void Clear()
+    {
+        _items.Clear();
+        _containers.Clear();
+    }
+}