refactor: clean up scenes and introduce SceneKey enum

- Remove redundant `GameFlowScene` and `PlaceholderEncounterScene`
- Introduce `SceneKey` enum for type-safe scene management
- Clean up unused imports and configuration references in existing
  scenes
- Standardize scene navigation using `SceneKey`

packages/sts-like-viewer/src/scenes/GridViewerScene.ts

@@ -1,7 +1,6 @@
-import Phaser from "phaser";
 import { ReactiveScene } from "boardgame-phaser";
 import { createButton } from "@/utils/createButton";
-import { GRID_CONFIG, UI_CONFIG, ITEM_COLORS } from "@/config";
+import { GRID_CONFIG, ITEM_COLORS } from "@/config";
 import {
   createGridInventory,
   placeItem,
@@ -12,6 +11,7 @@ import {
   type InventoryItem,
   type GameItemMeta,
 } from "boardgame-core/samples/slay-the-spire-like";
+import { SceneKey } from "./types";
 
 export class GridViewerScene extends ReactiveScene {
   private inventory: GridInventory<GameItemMeta>;
@@ -57,7 +57,7 @@ export class GridViewerScene extends ReactiveScene {
   }
 
   private placeSampleItems(): void {
-    const items = data.desert.items;
+    const items = data.desert.getItems();
     const sampleItems = [
       { index: 0, x: 0, y: 0 },
       { index: 3, x: 3, y: 0 },
@@ -207,7 +207,7 @@ export class GridViewerScene extends ReactiveScene {
       x: 100,
       y: 40,
       onClick: async () => {
-        await this.sceneController.launch("IndexScene");
+        await this.sceneController.launch(SceneKey.IndexScene);
       },
     });
 
@@ -242,7 +242,7 @@ export class GridViewerScene extends ReactiveScene {
       GRID_CONFIG.WIDTH,
       GRID_CONFIG.HEIGHT,
     );
-    const items = data.desert.items;
+    const items = data.desert.getItems();
 
     let itemIndex = 0;
     for (let y = 0; y < GRID_CONFIG.HEIGHT && itemIndex < items.length; y++) {