chore(core): bump zod to ^3.25.76

为即将引入的 InkosProvider / InkosModel zod schema（Task A2）做准备。
zod 3.25+ 有更好的 readonly/deep-partial 类型推导。

packages/core/package.json

@@ -50,7 +50,7 @@
     "dotenv": "^16.4.0",
     "epub-gen-memory": "^1.0.10",
     "js-yaml": "^4.1.1",
-    "zod": "^3.24.0"
+    "zod": "^3.25.76"
   },
   "devDependencies": {
     "@types/js-yaml": "^4.0.9",

pnpm-lock.yaml

@@ -85,7 +85,7 @@ importers:
         specifier: ^4.1.1
         version: 4.1.1
       zod:
-        specifier: ^3.24.0
+        specifier: ^3.25.76
         version: 3.25.76
     devDependencies:
       '@types/js-yaml':