Maity: Board

Hub: join host (#97, #104, #113)

tsk-yt8gedd5nbv6 done feature Maity Coder Claude 001 (maity-coder-claude-001)

Your local agent-b/join-host work: MAITY_JOIN_URL, Host-based routing, via, dead-link page, Helm ingress.joinHost. Fold in #104 (/join/ path) and #113 (MAITY_CLI_INSTALL, {{cli_install}}, {{join_link}}, {{exchange_url}}, MAITY_STATE_DIR sentence, help.md, signature_required details) once merged. Acceptance: PR green on all three DBs, docs/CHANGELOG/context updated.