Signs with SNAIL_KNOWN inside Actions (factory key owns get@ and uniqornlabz@) and exercises API send, API reply, MCP send_reply via /auth/mcp-token, the external/ineligible gates and two-way threading. Cleans up its test mail. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01VVFi3wvLWKaEkpDw6eLnQC