React Component Refactoring & Unit Test Generation

Please review, refactor, and generate comprehensive unit tests for this React component.

### Component Details
- **Component Name**: UserProfileCard
- **Target Test Runner & Library**: Vitest + React Testing Library
- **Primary Refactoring Priority**: Clean Architecture & Custom Hook Extraction

### Current Component Code
```tsx
import React, { useState, useEffect } from 'react';

export function UserProfileCard({ userId }) {
  const [user, setUser] = useState(null);
  const [loading, setLoading] = useState(true);
  const [editing, setEditing] = useState(false);
  const [name, setName] = useState('');

  useEffect(() => {
    fetch('/api/users/' + userId)
      .then(res => res.json())
      .then(data => {
        setUser(data);
        setName(data.name);
        setLoading(false);
      });
  }, [userId]);

  if (loading) return <div>Loading...</div>;

  return (
    <div className="card">
      {editing ? (
        <input value={name} onChange={e => setName(e.target.value)} />
      ) : (
        <h3>{user.name}</h3>
      )}
      <button onClick={() => setEditing(!editing)}>
        {editing ? 'Save' : 'Edit'}
      </button>
    </div>
  );
}
```

### Instructions for Refactoring
1. **Architecture & Decomposition**:
   - Extract stateful business logic into a custom hook or pure helper functions if appropriate.
   - Eliminate unnecessary re-renders, duplicate state derivations, and risky `useEffect` triggers.
2. **Accessibility & Semantics**:
   - Ensure semantic HTML, appropriate `aria-*` attributes, keyboard navigation (Enter, Space, Escape, Tab), and visible focus indicators.
3. **TypeScript Typing**:
   - Provide explicit interfaces for all props, event handlers, and data structures. Avoid implicit any.

### Instructions for Test Generation
1. Write a complete, copy-ready test file using **Vitest + React Testing Library**.
2. Cover:
   - Happy path rendering with default props.
   - User interactions (clicking, keyboard accessibility, typing).
   - Loading states, empty states, and error handling.
   - Asynchronous updates and cleanup.
3. Use accessible Testing Library query selectors (e.g., `getByRole`, `getByLabelText`) over test IDs or CSS classes.