Improved copy/export options

[parsapanahpoor]

• Issue Title: Enhance copy and export options for JSON and nodes
• Description:
  Extend the existing copy/export functionality to support copying a node or subtree as JSON, and exporting either the whole document or a selected part with pretty-print or minified formats.
• Tasks:
  • Add option to copy a single node or subtree as JSON.
  • Support copy/export of full JSON in pretty/minified modes.
  • Expose configuration for which copy/export options are visible.
  • Ensure exported JSON is always valid and uses current state.
  • Add documentation and examples.