<!-- source-hash: 786a6c83f7b7be019293590b300def02 -->
Provides a React-version-aware helper that returns the correct prop shape for the HTML `fetchpriority` attribute, avoiding console warnings across React 18 and React 19+.

## Key Components

| Export | Type | Description |
|--------|------|-------------|
| `FetchPriorityValue` | `type` | Union of valid HTML fetch-priority strings: `'high' \| 'low' \| 'auto'` |
| `fetchPriorityProp()` | `function` | Returns `{ fetchpriority: value }` (React 18) or `{ fetchPriority: value }` (React 19+) |
| `REACT_MAJOR` | internal `const` | Major version parsed from `React.version` at module load |
| `USE_CAMEL_CASE_FETCH_PRIORITY` | internal `const` | `true` when React major ≥ 19 |

## Behavior

- **`undefined`** → resolves to `'auto'` (DOM default), safe to spread without null-checking at each callsite
- **`true`** → `'high'` (intended for LCP candidates)
- **`false`** → `'low'`
- **`'high' | 'low' | 'auto'`** → passed through as-is

## Usage Example

```typescript
import { fetchPriorityProp } from './fetch-priority';

// Boolean shorthand — LCP hero image
<img
  src="/hero.jpg"
  alt="Hero"
  {...fetchPriorityProp(true)}   // React 18: { fetchpriority: "high" }
                                 // React 19: { fetchPriority: "high" }
/>

// Explicit value
<iframe
  src="/embed"
  {...fetchPriorityProp('low')}
/>

// Optional prop — undefined safely becomes 'auto'
<img src={src} {...fetchPriorityProp(maybeHigh)} />
```