fix(graphics): tune presets, single-line ui, vegetation LOD by nearest instance

- Bump high to 30m chunk / HD<20m and ultra to HD<30m so HD models
  persist further before swapping.
- Render the 5 graphics preset cards on a single row.
- Vegetation LOD selection now uses the distance to the nearest instance
  in each chunk instead of the chunk centre, matching MapInstancingSystem
  and avoiding premature LOD swaps when the camera enters a chunk.

src/data/world/graphicsConfig.ts

@@ -39,12 +39,12 @@ export const GRAPHICS_PRESETS = {
   },
   high: {
     label: "High",
-    chunkLoadRadius: 35,
-    chunkUnloadRadius: 45,
+    chunkLoadRadius: 30,
+    chunkUnloadRadius: 40,
     chunkStreamingEnabled: true,
     fogEnabled: false,
     forceLodModels: false,
-    lodHighDetailDistance: 10,
+    lodHighDetailDistance: 20,
   },
   ultra: {
     label: "Ultra",
@@ -53,7 +53,7 @@ export const GRAPHICS_PRESETS = {
     chunkStreamingEnabled: true,
     fogEnabled: false,
     forceLodModels: false,
-    lodHighDetailDistance: 20,
+    lodHighDetailDistance: 30,
   },
   max: {
     label: "Max",