Adds the native WinUI A2UI rendering pipeline, MCP/local security hardening, navigation/media safeguards, and integration/UI coverage for tray-hosted A2UI surfaces.\n\nThanks to @codemonkeychris for the substantial implementation and follow-through on review feedback.\n\nCo-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
