Add a copy button for tables with Markdown and CSV formats

## Feature request

Add a copy button above each table, aligned to the top-right corner.

The button must let users copy the complete table in either of these formats:

- Markdown
- CSV

## Acceptance criteria

- Each table shows a copy control in its top-right area.
- The control lets the user select Markdown or CSV.
- The copied content includes all table headers and rows.
- The Markdown output uses a valid Markdown table format.
- The CSV output correctly escapes commas, quotation marks, and line breaks.
- The interface shows a clear success or error message after a copy action.
- Users can operate the control with a keyboard and a screen reader.

No source file, test, or entry point is named in the issue; start by locating the component that renders tables. Verify the copy control supports Markdown and CSV, includes all headers and rows, escapes CSV values correctly, and reports success or failure. Done means keyboard and screen-reader users can operate it and every table exposes the control in the top-right area.

Written by the indexing model from the issue text.