<!-- source-hash: 4c976421380cc16af600736693d5afa7 -->
A client-side React component providing a drag-and-drop file upload zone with support for both simple synchronous file handling and async managed upload workflows (e.g., presigned URL uploads).

## Key Components

### Interfaces

- **`ManagedFileEntry`** — Represents an async upload entry with `id`, `fileName`, `fileSize`, `status` (`"uploading" | "uploaded" | "error"`), and optional `error` message.
- **`FileUploadProps`** — Full prop surface for the component, supporting both simple (`value`/`onChange`) and managed (`managedFiles`/`onRemoveManagedFile`) modes.

### Internal Utilities

- **`formatFileSize(bytes)`** — Converts byte count to a human-readable string (B, KB, MB, GB).
- **`matchesAccept(file, accept)`** — Validates a `File` against an `accept` string (extension, wildcard MIME, or exact MIME).
- **`dragHasFiles(e)`** — Checks whether a native `DragEvent` carries file payloads.

### Component

- **`FileUpload`** — Main export. Renders a dropzone with file list, validation, and optional window-level drop capture.

## Usage Example

```typescript
// Simple mode — synchronous, single file
<FileUpload
  value={file}
  onChange={(f) => setFile(f as File)}
  accept="image/*"
  maxSize={5 * 1024 * 1024}
  fieldLabel="Attachment"
/>

// Managed mode — async upload workflow
<FileUpload
  managedFiles={uploadedFiles}
  onChange={(files) => uploadToPresignedUrl(files as File[])}
  onRemoveManagedFile={(id) => removeFile(id)}
  onDownloadManagedFile={(id) => downloadFile(id)}
  multiple
  accept=".pdf,.doc,.docx"
  maxFiles={5}
  acceptWindowDrops  // captures drops anywhere in the window
/>
```

## Key Behaviors

| Feature | Detail |
|---|---|
| Mode detection | `managedFiles !== undefined` switches to managed mode |
| Validation | Type, size, and count checks before `onChange` fires |
| Window drops | `acceptWindowDrops` suppresses browser default and routes drops here |
| Single-file mode | Dropzone hides after a file is selected |
| Scroll cap | `maxListHeight` constrains the file list with independent scroll |