feat(A.5 T1): LandblockStreamTier + LandblockStreamJobKind enums

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

src/AcDream.App/Streaming/LandblockStreamTier.cs

@@ -0,0 +1,28 @@
+namespace AcDream.App.Streaming;
+
+/// <summary>
+/// Streaming-tier classification for a landblock. <see cref="Far"/> means
+/// terrain mesh only; <see cref="Near"/> means terrain + scenery + EnvCells +
+/// entity registration with the WB dispatcher. Per Phase A.5 spec §3.
+/// </summary>
+public enum LandblockStreamTier
+{
+    Far,
+    Near,
+}
+
+/// <summary>
+/// What work the streaming worker should perform for a given job. Distinct
+/// from <see cref="LandblockStreamTier"/> because <see cref="PromoteToNear"/>
+/// reads only the entity layer (terrain mesh already loaded), while
+/// <see cref="LoadNear"/> reads everything from scratch. Per Phase A.5 spec §4.3.
+/// </summary>
+public enum LandblockStreamJobKind
+{
+    /// <summary>Read LandBlock heightmap, build mesh, no entity layer.</summary>
+    LoadFar,
+    /// <summary>Read LandBlock + LandBlockInfo, generate scenery, build mesh, full entity layer.</summary>
+    LoadNear,
+    /// <summary>Read LandBlockInfo + scenery only — terrain already loaded for this LB.</summary>
+    PromoteToNear,
+}