refactor nav coverage into clustered windows

Replace region-based runtime pathing with interest-cluster coverage windows so active nav areas stay contiguous and spawn anchors participate in initial coverage.

Assets/Features/VoxelWorld/Contracts/NavMeshWorldContracts.cs

@@ -17,6 +17,12 @@ namespace InfiniteWorld.VoxelWorld.Contracts
         void GetInterestPoints(List<WorldInterestPoint> results);
     }
 
+    public interface INavCoverageReader
+    {
+        bool IsPositionCovered(Vector3 worldPosition);
+        void GetCoverageWindows(List<NavCoverageWindowSnapshot> results);
+    }
+
     public readonly struct ChunkNavSourceSnapshot
     {
         public ChunkNavSourceSnapshot(Vector2Int coord, int version, ChunkNavBuildSourceDescriptor[] sources)
@@ -77,7 +83,31 @@ namespace InfiniteWorld.VoxelWorld.Contracts
     {
         PlayerActor = 0,
         ActiveNpc = 1,
-        Other = 2
+        SpawnAnchor = 2,
+        Other = 3
+    }
+
+    public readonly struct NavCoverageWindowSnapshot
+    {
+        public NavCoverageWindowSnapshot(int id, Bounds bounds, NavCoverageState state, int interestCount)
+        {
+            Id = id;
+            Bounds = bounds;
+            State = state;
+            InterestCount = interestCount;
+        }
+
+        public int Id { get; }
+        public Bounds Bounds { get; }
+        public NavCoverageState State { get; }
+        public int InterestCount { get; }
+    }
+
+    public enum NavCoverageState
+    {
+        Pending = 0,
+        Building = 1,
+        Ready = 2
     }
 
     public readonly struct ChunkNavGeometryReadyMessage

Assets/Features/VoxelWorld/Prefabs/VoxelWorld.prefab

@@ -83,8 +83,12 @@ MonoBehaviour:
   worldGenerator: {fileID: 2927522923773808063}
   config:
     agentTypeId: 0
-    navRegionSizeInChunks: 2
     maxNavMeshBuildsPerFrame: 1
     navBoundsHorizontalPadding: 1
     navBoundsVerticalPadding: 2
-    navWarmupRadiusInRegions: 1
+    maxActiveCoverageWindows: 3
+    clusterMergeDistanceInChunks: 4
+    coveragePaddingInChunks: 2
+    coverageQuantizationInChunks: 1
+    minCoverageWindowSizeInChunks: 4
+    chunkCollectionMarginInChunks: 1

Assets/Features/VoxelWorld/Scenes/VoxelWorldTestScene.unity

@@ -255,6 +255,7 @@ GameObject:
   serializedVersion: 6
   m_Component:
   - component: {fileID: 171707223}
+  - component: {fileID: 171707224}
   m_Layer: 0
   m_Name: SpawnPoint
   m_TagString: Untagged
@@ -277,6 +278,19 @@ Transform:
   m_Children: []
   m_Father: {fileID: 0}
   m_LocalEulerAnglesHint: {x: 0, y: 0, z: 0}
+--- !u!114 &171707224
+MonoBehaviour:
+  m_ObjectHideFlags: 0
+  m_CorrespondingSourceObject: {fileID: 0}
+  m_PrefabInstance: {fileID: 0}
+  m_PrefabAsset: {fileID: 0}
+  m_GameObject: {fileID: 171707222}
+  m_Enabled: 1
+  m_EditorHideFlags: 0
+  m_Script: {fileID: 11500000, guid: 7a0a7758ae4541b39ed0b5d1fe912869, type: 3}
+  m_Name: 
+  m_EditorClassIdentifier: Assembly-CSharp::VoxelWorldScene.VoxelWorldSpawnAnchor
+  priority: 2
 --- !u!1001 &1165873058
 PrefabInstance:
   m_ObjectHideFlags: 0