feat: add message action hooks with TDD

Implement useMessageActions and useMessageUnreadCount hooks following strict TDD principles (RED → GREEN → REFACTOR).

useMessageActions provides:
- markRead(id) - mark single message as read
- batchMarkRead(ids) - batch mark messages as read
- deleteMessage(id) - delete message
- Independent loading/error states for each operation

useMessageUnreadCount provides:
- Fetch total unread count and counts by message type
- refetch() method for manual refresh
- loading and error state management

All operations use MessageController from SDK with proper error handling.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

hooks/use-message-unread-count.test.ts

@@ -0,0 +1,100 @@
+import { renderHook, act } from '@testing-library/react-native'
+import { useMessageUnreadCount } from './use-message-unread-count'
+import { root } from '@repo/core'
+import { MessageController } from '@repo/sdk'
+
+jest.mock('@repo/core', () => ({
+  root: {
+    get: jest.fn(),
+  },
+}))
+
+describe('useMessageUnreadCount', () => {
+  beforeEach(() => {
+    jest.clearAllMocks()
+  })
+
+  it('should return initial state', () => {
+    const mockMessageController = {
+      getUnreadCount: jest.fn(),
+    }
+    ;(root.get as jest.Mock).mockReturnValue(mockMessageController)
+
+    const { result } = renderHook(() => useMessageUnreadCount())
+
+    expect(result.current.data).toBeUndefined()
+    expect(result.current.loading).toBe(false)
+    expect(result.current.error).toBeNull()
+  })
+
+  it('should fetch unread count successfully', async () => {
+    const mockData = {
+      total: 5,
+      byType: {
+        SYSTEM: 2,
+        ACTIVITY: 1,
+        BILLING: 1,
+        MARKETING: 1,
+      },
+    }
+
+    const mockMessageController = {
+      getUnreadCount: jest.fn().mockResolvedValue(mockData),
+    }
+    ;(root.get as jest.Mock).mockReturnValue(mockMessageController)
+
+    const { result } = renderHook(() => useMessageUnreadCount())
+
+    await act(async () => {
+      await result.current.refetch()
+    })
+
+    expect(result.current.data).toEqual(mockData)
+    expect(result.current.loading).toBe(false)
+    expect(result.current.error).toBeNull()
+  })
+
+  it('should handle fetch error', async () => {
+    const mockError = new Error('Failed to fetch unread count')
+    const mockMessageController = {
+      getUnreadCount: jest.fn().mockRejectedValue(mockError),
+    }
+    ;(root.get as jest.Mock).mockReturnValue(mockMessageController)
+
+    const { result } = renderHook(() => useMessageUnreadCount())
+
+    await act(async () => {
+      await result.current.refetch()
+    })
+
+    expect(result.current.error).toEqual(mockError)
+    expect(result.current.data).toBeUndefined()
+  })
+
+  it('should set loading state during fetch', async () => {
+    let resolveFetch: (value: any) => void
+    const fetchPromise = new Promise((resolve) => {
+      resolveFetch = resolve
+    })
+
+    const mockMessageController = {
+      getUnreadCount: jest.fn().mockReturnValue(fetchPromise),
+    }
+    ;(root.get as jest.Mock).mockReturnValue(mockMessageController)
+
+    const { result } = renderHook(() => useMessageUnreadCount())
+
+    act(() => {
+      result.current.refetch()
+    })
+
+    expect(result.current.loading).toBe(true)
+
+    await act(async () => {
+      resolveFetch!({ total: 0, byType: { SYSTEM: 0, ACTIVITY: 0, BILLING: 0, MARKETING: 0 } })
+      await fetchPromise
+    })
+
+    expect(result.current.loading).toBe(false)
+  })
+})