feat(interact): Phase B.4 Use / UseWithTarget / TeleToLifestone outbound

Click-to-interact wire layer. Adds the three most common "do a thing
to an object" GameActions that the UI triggers on left-click / use-item
contexts.

Wire layer:
- InteractRequests.BuildUse (0x0036): single target guid — click a
  door, loot a corpse, talk to an NPC, activate a lifestone, step on
  a portal.
- InteractRequests.BuildUseWithTarget (0x0035): source + target —
  key on locked door, scroll on self, salvage tool on item.
- InteractRequests.BuildTeleToLifestone (0x0063): no-arg recall. Fails
  server-side if not tied; reply comes back as GameEvent WeenieError.

Server reply for Use + UseWithTarget is GameEventType.UseDone (0x01C7)
carrying a WeenieError code (0 = success). Already parsed; wiring
into a "UseDone" event on CombatState-style holder can be a follow-up.

Tests (3 new): byte-exact encoding of all three builders.

Build green, 616 tests pass (up from 613).

Ref: r08 §3 rows 0x0035/0x0036/0x0063.

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

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

@@ -0,0 +1,76 @@
+using System.Buffers.Binary;
+
+namespace AcDream.Core.Net.Messages;
+
+/// <summary>
+/// Outbound interaction GameActions. Each carries a single uint32
+/// target guid (plus a second guid for <c>UseWithTarget</c>) inside the
+/// standard <c>0xF7B1</c> GameAction envelope.
+///
+/// <para>
+/// Wire layout (r08 §3 rows 0x0035/0x0036):
+/// <code>
+///   u32 0xF7B1
+///   u32 gameActionSequence
+///   u32 subOpcode
+///   u32 targetGuid        // e.g. door, NPC, lifestone, corpse, item
+///   u32 sourceGuid        // only for UseWithTarget (the item you're using)
+/// </code>
+/// </para>
+///
+/// <para>
+/// Server reply is <c>GameEventType.UseDone</c> (0x01C7) carrying a
+/// <c>WeenieError</c>; 0 = success.
+/// </para>
+/// </summary>
+public static class InteractRequests
+{
+    public const uint GameActionEnvelope = 0xF7B1u;
+    public const uint UseOpcode = 0x0036u;
+    public const uint UseWithTargetOpcode = 0x0035u;
+    public const uint TeleToLifestoneOpcode = 0x0063u;
+
+    /// <summary>
+    /// Use an object: click a door, loot a corpse, talk to an NPC,
+    /// activate a lifestone, step onto a portal.
+    /// </summary>
+    public static byte[] BuildUse(uint gameActionSequence, uint targetGuid)
+    {
+        byte[] body = new byte[16];
+        BinaryPrimitives.WriteUInt32LittleEndian(body,            GameActionEnvelope);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(4),  gameActionSequence);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(8),  UseOpcode);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(12), targetGuid);
+        return body;
+    }
+
+    /// <summary>
+    /// Use source item on target: e.g. key on locked door, key on
+    /// chest, scroll on yourself, salvage tool on an item.
+    /// </summary>
+    public static byte[] BuildUseWithTarget(
+        uint gameActionSequence, uint sourceGuid, uint targetGuid)
+    {
+        byte[] body = new byte[20];
+        BinaryPrimitives.WriteUInt32LittleEndian(body,            GameActionEnvelope);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(4),  gameActionSequence);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(8),  UseWithTargetOpcode);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(12), sourceGuid);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(16), targetGuid);
+        return body;
+    }
+
+    /// <summary>
+    /// Teleport to your lifestone. No target guid — just tells the
+    /// server "recall me." Fails if you haven't tied to a lifestone
+    /// (server responds with a WeenieError).
+    /// </summary>
+    public static byte[] BuildTeleToLifestone(uint gameActionSequence)
+    {
+        byte[] body = new byte[12];
+        BinaryPrimitives.WriteUInt32LittleEndian(body,            GameActionEnvelope);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(4),  gameActionSequence);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(8),  TeleToLifestoneOpcode);
+        return body;
+    }
+}