fix #483: restore far terrain and close OVERHAUL with #484 deferred

src/AcDream.App/Rendering/Walk/WalkLandscapeAssembler.cs

@@ -75,8 +75,19 @@ public sealed class WalkLandscapeAssembler
         RefreshSlotIfWindowed(bx, by);
     }
 
+    /// <summary>Near-tier retirement retains terrain and its authored bounds.
+    /// A late building cleanup must not recreate a fully retired block.</summary>
+    public void ClearBuildings(uint landblockId)
+    {
+        (int bx, int by) = BlockCoords(landblockId);
+        if (!_blocks.TryGetValue((bx, by), out BlockData? data))
+            return;
+        data.Buildings = Array.Empty<WalkBuildingFactory.Entry>();
+        RefreshSlotIfWindowed(bx, by);
+    }
+
     /// <summary>Landblock retirement (<c>LandblockRenderPublisher
-    /// .RemoveBuildingRegistry</c>): drop this landblock's data. Safe to call
+    /// .RemoveTerrain</c>): drop this landblock's data. Safe to call
     /// on a landblock that never published (no-op).</summary>
     public void RetireLandblock(uint landblockId)
     {

src/AcDream.App/Streaming/LandblockBuild.cs

@@ -3,6 +3,9 @@ using AcDream.Core.World;
 
 namespace AcDream.App.Streaming;
 
+/// <summary>Authored terrain z-slab, independent of near-tier cell/building data.</summary>
+public readonly record struct LandblockTerrainBounds(float MaxZ, float MinZ);
+
 /// <summary>
 /// Complete CPU-side output of one streaming job. The worker owns this object
 /// until it posts the corresponding completion; the render thread then applies
@@ -12,7 +15,8 @@ public sealed record LandblockBuild(
     LoadedLandblock Landblock,
     EnvCellLandblockBuild? EnvCells = null,
     LandblockBuildOrigin Origin = default,
-    LandblockCollisionBuild? Collisions = null)
+    LandblockCollisionBuild? Collisions = null,
+    LandblockTerrainBounds TerrainBounds = default)
 {
     public uint LandblockId => Landblock.LandblockId;
 }

src/AcDream.App/Streaming/LandblockBuildFactory.cs

@@ -132,13 +132,15 @@ public sealed class LandblockBuildFactory
         {
             var heightmapOnly = _dats.Get<DatReaderWriter.DBObjs.LandBlock>(landblockId);
             if (heightmapOnly is null) return null;
+            (float maxZ, float minZ) = ComputeWalkZSlab(heightmapOnly.Height);
             return new AcDream.App.Streaming.LandblockBuild(
                 new AcDream.Core.World.LoadedLandblock(
                     landblockId,
                     heightmapOnly,
                     System.Array.Empty<AcDream.Core.World.WorldEntity>(),
                     AcDream.Core.World.PhysicsDatBundle.Empty),
-                Origin: request.Origin);   // far tier: no cells/buildings/entities
+                Origin: request.Origin,
+                TerrainBounds: new(maxZ, minZ));   // far tier: no cells/buildings/entities
         }
 
         var baseLoaded = AcDream.Core.World.LandblockLoader.Load(_dats, landblockId);
@@ -179,7 +181,7 @@ public sealed class LandblockBuildFactory
                         _heightTable));
         var envCellBuild = new AcDream.App.Rendering.Wb.EnvCellLandblockBuildBuilder(landblockId);
         // Campaign FW3.1: the walk landscape's per-block z-slab
-        // (CLandBlock::calc_lighting-adjacent unpack @0x0052f1d0). Every
+        // (CLandBlock::get_land_limits @0x0052f1d0). Every
         // near-tier landblock has outdoor terrain heights regardless of
         // whether it has interior cells or buildings, so this is
         // unconditional — unlike WalkBuildings (added below, inside
@@ -208,7 +210,8 @@ public sealed class LandblockBuildFactory
                 merged,
                 physicsDats),
             completedEnvCells,
-            request.Origin);
+            request.Origin,
+            TerrainBounds: new(walkMaxZ, walkMinZ));
     }
     /// <summary>
     /// Phase A.1 Task 8: generate scenery (trees, rocks, bushes) for a single
@@ -673,7 +676,7 @@ public sealed class LandblockBuildFactory
 
     /// <summary>Campaign FW3.1: retail's per-block z-slab
     /// (<c>WalkLandscapeDatBuilder</c>'s port target —
-    /// <c>CLandBlock::calc_lighting</c>-adjacent unpack @0x0052f1d0):
+    /// <c>CLandBlock::get_land_limits</c> @0x0052f1d0):
     /// <c>max_zval = heightTable[maxByte] + 200</c>,
     /// <c>min_zval = heightTable[minByte] - 1</c>, over the landblock's own
     /// 81-byte heightmap. Uses <see cref="_heightTable"/> — already a

src/AcDream.App/Streaming/LandblockPresentationPipeline.cs

@@ -479,18 +479,18 @@ public sealed class LandblockPresentationPipeline
                 completed.Heightmap,
                 Array.Empty<WorldEntity>(),
                 PhysicsDatBundle.Empty);
+            LandblockBuild farBuild = new(
+                farLandblock,
+                Origin: completedBuild.Origin,
+                TerrainBounds: completedBuild.TerrainBounds);
             transaction = new PublicationTransaction
             {
                 Kind = PublicationKind.Far,
-                Build = new LandblockBuild(
-                    farLandblock,
-                    Origin: completedBuild.Origin),
+                Build = farBuild,
                 MeshData = meshData,
                 LandblockId = farLandblock.LandblockId,
                 Cost = LandblockStreamResultCost.Estimate(
-                    new LandblockBuild(
-                        farLandblock,
-                        Origin: completedBuild.Origin),
+                    farBuild,
                     meshData),
                 Tier = LandblockStreamTier.Far,
                 Timing = PublicationTimingProbe.CreateTimings(),
@@ -534,7 +534,8 @@ public sealed class LandblockPresentationPipeline
                 PhysicsDatBundle.Empty);
             LandblockBuild farBuild = new(
                 farLandblock,
-                Origin: completedBuild.Origin);
+                Origin: completedBuild.Origin,
+                TerrainBounds: completedBuild.TerrainBounds);
             transaction = new PublicationTransaction
             {
                 Kind = PublicationKind.Far,

src/AcDream.App/Streaming/LandblockRenderPublisher.cs

@@ -103,15 +103,9 @@ public sealed class LandblockRenderPublisher
     private readonly Action<EnvCellLandblockBuild>? _prepareEnvCells;
     private readonly Action<uint>? _removeEnvCells;
     private readonly Dictionary<uint, BuildingRegistry> _buildingRegistries = new();
-    // Campaign FW3.1: the walk's production world-data siblings of
-    // _buildingRegistries. Owned here (not injected) exactly like
-    // _buildingRegistries — no caller constructs a LandblockRenderPublisher
-    // with pre-existing walk state. Committed/retired at the same points as
-    // the building registry (see AdvanceCompleteOne / RemoveBuildingRegistry
-    // below) because both come from the same landblock's BuildingInfo array
-    // at the same commit. No frame reads these yet (FW3.2 wires the walk
-    // into the render loop) — publication happens now so FW3.1's
-    // conformance gate exercises the production commit path.
+    // The frame walk's sole terrain/building owners. Both publish in the
+    // retained render suffix; near-layer retirement clears only buildings,
+    // while full terrain retirement removes the landscape entry as well.
     private readonly WalkBuildingRegistry _walkBuildingRegistry = new();
     private readonly WalkLandscapeAssembler _walkLandscape = new();
 
@@ -360,21 +354,19 @@ public sealed class LandblockRenderPublisher
                 _buildingRegistries[registryKey] =
                     completedBuildings.Registry;
             }
-            // Campaign FW3.1: publish this landblock's walk world data in
-            // the same step — build.EnvCells carries WalkBuildings/WalkMaxZ
-            // /WalkMinZ (computed worker-side by LandblockBuildFactory) for
-            // every near-tier build, even one with zero interior cells
-            // (the z-slab is unconditional; WalkBuildings is naturally empty
-            // when LandBlockInfo has none).
+            // Terrain exists at both tiers; only near builds supply buildings.
+            // Keep both publications in this retained receipt's existing step.
             if (build.EnvCells is { } walkEnvCells)
-            {
                 _walkBuildingRegistry.Publish(landblockId, walkEnvCells.WalkBuildings);
-                _walkLandscape.PublishLandblock(
-                    landblockId,
-                    walkEnvCells.WalkMaxZ,
-                    walkEnvCells.WalkMinZ,
-                    walkEnvCells.WalkBuildings);
-            }
+            else
+                _walkBuildingRegistry.Retire(landblockId);
+            _walkLandscape.PublishLandblock(
+                landblockId,
+                build.TerrainBounds.MaxZ,
+                build.TerrainBounds.MinZ,
+                build.EnvCells is { } cells
+                    ? cells.WalkBuildings
+                    : Array.Empty<WalkBuildingFactory.Entry>());
             publication.BuildingRegistryCommitted = true;
         }
         else if (publication.EnvCellPublication is { } envCellPublication
@@ -421,6 +413,7 @@ public sealed class LandblockRenderPublisher
     public void RemoveTerrain(uint landblockId)
     {
         _removeTerrain(landblockId);
+        _walkLandscape.RetireLandblock(landblockId);
         _terrainRemovalCount++;
     }
 
@@ -433,14 +426,9 @@ public sealed class LandblockRenderPublisher
     public void RemoveBuildingRegistry(uint landblockId)
     {
         _buildingRegistries.Remove(landblockId & 0xFFFF0000u);
-        // Campaign FW3.1: retire the walk's siblings at the SAME retirement
-        // stage — they were committed together above, so they retire
-        // together (no new LandblockRetirementStage; folding into the
-        // existing BuildingRegistry stage keeps the retirement ticket state
-        // machine unchanged, which is the minimal/additive choice for a
-        // slice that does no frame wiring yet).
+        // Demotion retires buildings, not the retained far-tier terrain.
         _walkBuildingRegistry.Retire(landblockId);
-        _walkLandscape.RetireLandblock(landblockId);
+        _walkLandscape.ClearBuildings(landblockId);
         _buildingRegistryRemovalCount++;
     }
 

src/AcDream.App/Streaming/LandblockStreamer.cs

@@ -615,7 +615,10 @@ public sealed class LandblockStreamer : IDisposable, ILandblockCompletionSource
                             lb.Heightmap,
                             System.Array.Empty<AcDream.Core.World.WorldEntity>(),
                             PhysicsDatBundle.Empty);
-                        build = new LandblockBuild(lb, Origin: build.Origin);
+                        build = new LandblockBuild(
+                            lb,
+                            Origin: build.Origin,
+                            TerrainBounds: build.TerrainBounds);
                     }
                     PublishResult(new LandblockStreamResult.Loaded(
                         load.LandblockId, tier, build, mesh, load.Generation));