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;
+    }
+}