ScreenboardModal class

ScreenboardModal - A modal component for managing screen annotation overlays.

This component replicates React's ScreenboardModal approach:

• On web: Combines screen video + annotation canvas into a single MediaStream
• Uses HTML video/canvas elements for capture (web only)
• Sends the combined stream via WebRTC to broadcast annotations

Key Features:

• Annotation Broadcasting (Web): Combines screen share with annotations
• Stream Management: Handles local screen stream and processed stream
• Canvas Integration: Manages canvas for annotation rendering
• Transport Lifecycle: Creates, connects, and disconnects WebRTC transport
• Modal Controls: Close button with automatic cleanup

Example:

ScreenboardModal(
  options: ScreenboardModalOptions(
    parameters: screenboardParameters,
    isVisible: true,
    onClose: () => setState(() => isModalVisible = false),
  ),
)