docs(agile): initialize docs

docs/architecture/state-management.md

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+# 5. State Management
+
+*   **Approach:** For the MVP, we will rely primarily on **Nuxt's built-in `useState` composable** for simple, shared, server-side-renderable state. This is the most lightweight and idiomatic approach for Nuxt 4. We will avoid installing a heavy external library like Pinia or Vuex until the application's complexity demonstrably requires it.
+*   **Structure:** Shared state composables will be located in the `app/composables/` directory.
+
+## State Management Template (`app/composables/useSomeState.ts`)
+
+```typescript
+import { useState } from '#app';
+
+// Example: Managing the current Citizen's session info
+interface CitizenSession {
+  name: string;
+  publicKey: string;
+  // NOTE: The private key should NOT be stored in a composable.
+  // It should be managed in a more secure, non-persistent way.
+}
+
+export const useCitizenStore = () => {
+  const citizen = useState<CitizenSession | null>('citizen', () => null);
+
+  const setCitizen = (newCitizen: CitizenSession) => {
+    citizen.value = newCitizen;
+  };
+
+  const clearCitizen = () => {
+    citizen.value = null;
+  };
+
+
+
+  return {
+    citizen,
+    setCitizen,
+    clearCitizen,
+  };
+};
+```
+
+---