feat(vegetation): wire arbre/sapin/buisson into LOD system

Register the three new vegetation LOD models in MAP_LOD_MODEL_PATHS and
extend VegetationSystem with per-chunk distance-based LOD selection
(mirroring MapInstancingSystem). Chunk model paths are re-evaluated on
the existing CHUNK_CONFIG.updateInterval cadence and Suspense keys
include the resolved path so a swap unmounts the previous instanced mesh
cleanly.

src/data/world/mapLodConfig.ts

@@ -14,6 +14,9 @@ export const MAP_LOD_MODEL_PATHS = {
   maison1: "/models/maison1-LOD/model.gltf",
   panneauaffichage: "/models/panneauaffichage-LOD/model.gltf",
   talkie: "/models/talkie-LOD/model.gltf",
+  arbre: "/models/arbre-LOD/model.glb",
+  buisson: "/models/buisson-LOD/model.glb",
+  sapin: "/models/sapin-LOD/model.glb",
 } as const satisfies Record<string, string>;
 
 export function getMapLodModelPath(modelName: string): string | null {

src/world/vegetation/VegetationSystem.tsx

@@ -1,8 +1,20 @@
-import { Suspense, useMemo } from "react";
+import {
+  Suspense,
+  useCallback,
+  useEffect,
+  useMemo,
+  useRef,
+  useState,
+} from "react";
+import { useFrame, useThree } from "@react-three/fiber";
 import { CHUNK_CONFIG } from "@/data/world/chunkStreamingConfig";
+import { selectMapModelPathByDistance } from "@/data/world/mapLodConfig";
 import { useCameraMode } from "@/hooks/debug/useCameraMode";
 import { useSceneMode } from "@/hooks/debug/useSceneMode";
-import { useGraphicsPresetConfig } from "@/hooks/world/useGraphicsSettings";
+import {
+  useGraphicsPreset,
+  useGraphicsPresetConfig,
+} from "@/hooks/world/useGraphicsSettings";
 import { useVisibleWorldChunks } from "@/hooks/world/useVisibleWorldChunks";
 import {
   isMapModelVisible,
@@ -18,6 +30,7 @@ import {
 } from "@/data/world/vegetationConfig";
 import { isInsideLaFabrikFootprint } from "@/data/world/laFabrikConfig";
 import { createWorldInstanceChunks } from "@/utils/world/chunkInstances";
+import type { GraphicsPreset } from "@/data/world/graphicsConfig";
 
 interface VegetationSystemProps {
   onlyMapName?: string | null;
@@ -70,12 +83,73 @@ function removeLaFabrikVegetation(
   });
 }
 
+function areChunkModelPathsEqual(
+  a: ReadonlyMap<string, string>,
+  b: ReadonlyMap<string, string>,
+): boolean {
+  return (
+    a.size === b.size && [...a].every(([key, value]) => b.get(key) === value)
+  );
+}
+
+function useVegetationChunkModelPaths(
+  chunks: readonly VegetationChunk[],
+  preset: GraphicsPreset,
+): ReadonlyMap<string, string> {
+  const camera = useThree((state) => state.camera);
+  const lastUpdateRef = useRef(-CHUNK_CONFIG.updateInterval);
+  const modelPathsRef = useRef<Map<string, string>>(new Map());
+  const [modelPaths, setModelPaths] = useState<ReadonlyMap<string, string>>(
+    () => new Map(),
+  );
+
+  const updateModelPaths = useCallback(() => {
+    const cameraX = camera.position.x;
+    const cameraZ = camera.position.z;
+    const next = new Map<string, string>();
+
+    for (const chunk of chunks) {
+      const distance = Math.hypot(
+        chunk.centerX - cameraX,
+        chunk.centerZ - cameraZ,
+      );
+      const modelPath = selectMapModelPathByDistance({
+        distance,
+        modelName: VEGETATION_TYPES[chunk.type].mapName,
+        modelPath: chunk.modelPath,
+        preset,
+      });
+      next.set(chunk.key, modelPath);
+    }
+
+    if (areChunkModelPathsEqual(next, modelPathsRef.current)) return;
+
+    modelPathsRef.current = next;
+    setModelPaths(next);
+  }, [camera, chunks, preset]);
+
+  useEffect(() => {
+    updateModelPaths();
+  }, [updateModelPaths]);
+
+  useFrame(({ clock }) => {
+    const now = clock.elapsedTime * 1000;
+    if (now - lastUpdateRef.current < CHUNK_CONFIG.updateInterval) return;
+    lastUpdateRef.current = now;
+
+    updateModelPaths();
+  });
+
+  return modelPaths;
+}
+
 export function VegetationSystem({
   onlyMapName = null,
   streaming = true,
 }: VegetationSystemProps): React.JSX.Element | null {
   const cameraMode = useCameraMode();
   const sceneMode = useSceneMode();
+  const graphicsPresetKey = useGraphicsPreset();
   const graphicsPreset = useGraphicsPresetConfig();
   const groups = useMapPerformanceStore((state) => state.groups);
   const models = useMapPerformanceStore((state) => state.models);
@@ -113,16 +187,23 @@ export function VegetationSystem({
     unloadRadius: graphicsPreset.chunkUnloadRadius,
   });
 
+  const chunkModelPaths = useVegetationChunkModelPaths(
+    visibleChunks,
+    graphicsPresetKey,
+  );
+
   if (isLoading || !data) {
     return null;
   }
 
   return (
     <group name="vegetation-system">
-      {visibleChunks.map((chunk) => (
+      {visibleChunks.map((chunk) => {
-        <Suspense key={chunk.key} fallback={null}>
+        const modelPath = chunkModelPaths.get(chunk.key) ?? chunk.modelPath;
+        return (
+          <Suspense key={`${chunk.key}:${modelPath}`} fallback={null}>
             <InstancedVegetation
-            modelPath={chunk.modelPath}
+              modelPath={modelPath}
               instances={chunk.instances}
               scaleMultiplier={chunk.scaleMultiplier}
               castShadow={chunk.castShadow}
@@ -131,7 +212,8 @@ export function VegetationSystem({
               rotationOffset={chunk.rotationOffset}
             />
           </Suspense>
-      ))}
+        );
+      })}
     </group>
   );
 }