chore(store): use import.meta.env.DEV instead of process.env.NODE_ENV (P3-53)

Vite-native idiom; added vite/client triple-slash reference to env.d.ts
so TS knows about ImportMeta.env.

src/renderer/env.d.ts

@@ -1,3 +1,4 @@
+/// <reference types="vite/client" />
 import type { DesktopApi } from "@shared/contracts";
 
 declare global {

src/renderer/state/store.ts

@@ -39,7 +39,7 @@ export const useAppStore = create<AppState>()(
     })),
     {
       name: "AgentCompany",
-      enabled: process.env.NODE_ENV === "development",
+      enabled: import.meta.env.DEV,
     }
   )
 );