Makes copied review context more complete, predictable, and useful.

• Added stable handling for dynamically loaded and collapsed review comments.
• Made the Include in context checkbox the single source of truth.
• Defaulted resolved comments to unchecked while keeping them selectable.
• Added opt-in recursive loading for hidden review conversations.
• Grouped comments and replies from the same thread in copied markdown.
• Prevented GitHub search and command-palette behavior from leaking into the copy button.