fix: sync identity stores and append signatures to outgoing emails (#15)

- Add syncIdentities() to auth store to propagate identity changes from
  identity store, fixing stale data that caused save failures and duplicates
- Call syncIdentities() after every create, update, and delete in the
  identity manager modal
- Switch email composer to read identities from identity store for
  consistency with the rest of the app
- Append identity text signature (with RFC 3676 separator) to email body
  when sending from the composer and quick reply paths
- Add tests for syncIdentities and signature appending logic

stores/__tests__/auth-store-sync.test.ts

@@ -0,0 +1,112 @@
+import { describe, it, expect, beforeEach } from 'vitest';
+import { useAuthStore } from '../auth-store';
+import { useIdentityStore } from '../identity-store';
+import type { Identity } from '@/lib/jmap/types';
+
+const makeIdentity = (overrides: Partial<Identity> = {}): Identity => ({
+  id: 'id-1',
+  name: 'Test User',
+  email: 'test@example.com',
+  mayDelete: true,
+  ...overrides,
+});
+
+describe('auth-store syncIdentities', () => {
+  beforeEach(() => {
+    useIdentityStore.setState({
+      identities: [],
+      selectedIdentityId: null,
+      isLoading: false,
+      error: null,
+      subAddress: { recentTags: [], tagSuggestions: {} },
+    });
+    useAuthStore.setState({
+      identities: [],
+      primaryIdentity: null,
+    });
+  });
+
+  it('should copy identities from identity store to auth store', () => {
+    const identities = [
+      makeIdentity({ id: 'id-1', name: 'Alice' }),
+      makeIdentity({ id: 'id-2', name: 'Bob', email: 'bob@example.com' }),
+    ];
+    useIdentityStore.getState().setIdentities(identities);
+
+    useAuthStore.getState().syncIdentities();
+
+    expect(useAuthStore.getState().identities).toHaveLength(2);
+    expect(useAuthStore.getState().identities[0].name).toBe('Alice');
+    expect(useAuthStore.getState().identities[1].name).toBe('Bob');
+  });
+
+  it('should set primaryIdentity to first identity', () => {
+    const identities = [
+      makeIdentity({ id: 'id-1', name: 'Primary' }),
+      makeIdentity({ id: 'id-2', name: 'Secondary' }),
+    ];
+    useIdentityStore.getState().setIdentities(identities);
+
+    useAuthStore.getState().syncIdentities();
+
+    expect(useAuthStore.getState().primaryIdentity?.id).toBe('id-1');
+    expect(useAuthStore.getState().primaryIdentity?.name).toBe('Primary');
+  });
+
+  it('should set primaryIdentity to null when no identities', () => {
+    // Auth store starts with an identity
+    useAuthStore.setState({
+      identities: [makeIdentity()],
+      primaryIdentity: makeIdentity(),
+    });
+    useIdentityStore.getState().setIdentities([]);
+
+    useAuthStore.getState().syncIdentities();
+
+    expect(useAuthStore.getState().identities).toEqual([]);
+    expect(useAuthStore.getState().primaryIdentity).toBeNull();
+  });
+
+  it('should reflect identity store changes after addIdentity', () => {
+    useIdentityStore.getState().setIdentities([makeIdentity({ id: 'id-1' })]);
+    useAuthStore.getState().syncIdentities();
+    expect(useAuthStore.getState().identities).toHaveLength(1);
+
+    useIdentityStore.getState().addIdentity(makeIdentity({ id: 'id-2', email: 'new@example.com' }));
+    useAuthStore.getState().syncIdentities();
+
+    expect(useAuthStore.getState().identities).toHaveLength(2);
+  });
+
+  it('should reflect identity store changes after removeIdentity', () => {
+    useIdentityStore.getState().setIdentities([
+      makeIdentity({ id: 'id-1' }),
+      makeIdentity({ id: 'id-2' }),
+    ]);
+    useAuthStore.getState().syncIdentities();
+    expect(useAuthStore.getState().identities).toHaveLength(2);
+
+    useIdentityStore.getState().removeIdentity('id-1');
+    useAuthStore.getState().syncIdentities();
+
+    expect(useAuthStore.getState().identities).toHaveLength(1);
+    expect(useAuthStore.getState().identities[0].id).toBe('id-2');
+    expect(useAuthStore.getState().primaryIdentity?.id).toBe('id-2');
+  });
+
+  it('should reflect identity store changes after updateIdentityLocal', () => {
+    useIdentityStore.getState().setIdentities([
+      makeIdentity({ id: 'id-1', name: 'Old Name', textSignature: '' }),
+    ]);
+    useAuthStore.getState().syncIdentities();
+
+    useIdentityStore.getState().updateIdentityLocal('id-1', {
+      name: 'New Name',
+      textSignature: 'Regards, Me',
+    });
+    useAuthStore.getState().syncIdentities();
+
+    expect(useAuthStore.getState().identities[0].name).toBe('New Name');
+    expect(useAuthStore.getState().identities[0].textSignature).toBe('Regards, Me');
+  });
+});

stores/auth-store.ts

@@ -33,6 +33,7 @@ interface AuthState {
   logout: () => void;
   checkAuth: () => Promise<void>;
   clearError: () => void;
+  syncIdentities: () => void;
 }
 
 const ERROR_PATTERNS: Array<{ key: string; matches: string[] }> = [
@@ -479,6 +480,13 @@ export const useAuthStore = create<AuthState>()(
       },
 
       clearError: () => set({ error: null }),
+
+      syncIdentities: () => {
+        const identityState = useIdentityStore.getState();
+        const identities = identityState.identities;
+        const primaryIdentity = identities[0] ?? null;
+        set({ identities, primaryIdentity });
+      },
     }),
     {
       name: 'auth-storage',