fix(game): 移除不安全的类型转换并增加存档校验 (refs #7)

在 character.ts 中使用 flatMap 结合类型缩窄（null 检查），移除了对 DccFile 的强制类型转换，保证内部逻辑的编译期安全。在 save.ts 中增加了对背包数据的严格运行时有效性验证，避免由于恶意或破损存档导致的隐式游戏损坏，并用专用的反序列化测试覆盖新校验过程。

src/game/character.ts

@@ -189,10 +189,12 @@ export async function loadCharacterSheet(
       // the priority table is the authority on what covers what.
       const order = cofLayerOrder(cof, direction, index)
       const ordered = order
-        .map(layerIndex => { const sprite = sprites[layerIndex]; return { layerIndex, sprite } })
-        .filter(entry => entry.sprite !== null && entry.sprite !== undefined)
+        .flatMap(layerIndex => {
+          const sprite = sprites[layerIndex]
+          return sprite != null ? [{ layerIndex, sprite }] : []
+        })
       for (const entry of ordered) {
-        const sprite = entry.sprite as DccFile
+        const sprite = entry.sprite
         const dccDir = dir64ToDcc(dir64, sprite.directions.length)
         const layerDirection = sprite.directions[dccDir]
         const frame = layerDirection?.frames[index]

src/game/save.ts

@@ -133,7 +133,16 @@ export function parseSnapshot(text: string): GameSnapshot {
   if (candidate.world === undefined || typeof candidate.world.tick !== 'number') throw new Error('save has no world')
   if (candidate.world.player === undefined) throw new Error('save has no player')
   if (!Array.isArray(candidate.world.monsters)) throw new Error('save has no monster list')
-  if (candidate.inventory === undefined || !Array.isArray(candidate.inventory.placed)) throw new Error('save has no inventory')
+  if (candidate.inventory === undefined || typeof candidate.inventory.width !== 'number' || typeof candidate.inventory.height !== 'number') {
+    throw new Error('save has no inventory bounds')
+  }
+  if (!Array.isArray(candidate.inventory.placed)) throw new Error('save has no inventory')
+  for (const [index, entry] of candidate.inventory.placed.entries()) {
+    if (typeof entry !== 'object' || entry === null) throw new Error(`inventory placed item [${index}] is malformed`)
+    if (typeof (entry as any).x !== 'number') throw new Error(`inventory placed item [${index}] has invalid x`)
+    if (typeof (entry as any).y !== 'number') throw new Error(`inventory placed item [${index}] has invalid y`)
+    if (typeof (entry as any).item !== 'object' || (entry as any).item === null) throw new Error(`inventory placed item [${index}] has no item`)
+  }
   if (!Array.isArray(candidate.quests)) throw new Error('save has no quest log')
   // Older saves predate ground items; an absent list is treated as empty rather
   // than as corruption, so the version does not have to be bumped for a field
@@ -171,7 +180,7 @@ export function restoreSnapshot(
     // live world would otherwise leave the previous player list in place.
     world: rebindPlayer({ ...snapshot.world, monsters: [...snapshot.world.monsters], players: [], events: [] }),
     rngState: snapshot.rngState,
-    inventory: build.inventory(snapshot.inventory.width, snapshot.inventory.height, snapshot.inventory.placed as PlacedItem[]),
+    inventory: build.inventory(snapshot.inventory.width, snapshot.inventory.height, snapshot.inventory.placed),
     quests: build.quests(snapshot.quests),
     ground: snapshot.ground.map(entry => ({ x: entry.x, y: entry.y, item: entry.item })),
   }

tests/save-schema.test.ts

@@ -0,0 +1,27 @@
+import { describe, it, expect } from 'vitest'
+import { parseSnapshot } from '../src/game/save.ts'
+
+describe('parseSnapshot', () => {
+  it('rejects malformed placed items in inventory', () => {
+    const badSnapshot = {
+      version: 1,
+      rngState: 0,
+      world: {
+        tick: 0,
+        player: {},
+        monsters: [],
+      },
+      inventory: {
+        width: 10,
+        height: 4,
+        placed: [
+          { x: 1, y: 1 }, // Missing item
+        ]
+      },
+      quests: [],
+      ground: []
+    }
+    
+    expect(() => parseSnapshot(JSON.stringify(badSnapshot))).toThrow('inventory placed item [0] has no item')
+  })
+})