[ dwebxr/aegis ] feat: add Copy npub button to D2A Agent Card

Shows full npub in clipboard + brief tooltip flash on click,
while keeping the masked display as default.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
https://github.com/dwebxr/aegis/commit/a6e640ee745bb6816af5cdbfad2470db8017ecbe