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/Scenes/VoxelWorldTestScene.unity

@@ -255,6 +255,7 @@ GameObject:
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+  - component: {fileID: 171707224}
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@@ -277,6 +278,19 @@ Transform:
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   m_Father: {fileID: 0}
   m_LocalEulerAnglesHint: {x: 0, y: 0, z: 0}
+--- !u!114 &171707224
+MonoBehaviour:
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+  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
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   m_ObjectHideFlags: 0