fix: look up the scene at a position as the client does, in constant time

Chunk bounds span (width - 1) * scale; the nearest scene map cell is used and the far edge is kept one cell inside. Chunks are indexed by grid cell when they form a grid. Skipping reads instead of seeking, so a cut-off file can't seek past the end. Terrain mesh indices follow the vertex order.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

dZoneManager/dZoneManager.h

@@ -77,6 +77,11 @@ public:
 	 */
 	std::vector<LWOSCENEID> GetAdjacentScenes(LWOSCENEID sceneID) const;
 
+	/**
+	 * @brief (Re)builds the scene graph adjacency list from the loaded zone's scene transitions.
+	 */
+	void BuildSceneGraph();
+
 	// The world config should not be modified by a caller.
 	const WorldConfig& GetWorldConfig() {
 		if (!m_WorldConfig) LoadWorldConfig();
@@ -84,10 +89,6 @@ public:
 	};
 
 private:
-	/**
-	 * Builds the scene graph adjacency list from scene transitions
-	 */
-	void BuildSceneGraph();
 	/**
 	 * The starting unique mission ID.
 	 */