Maity: Board

Hub: group chats (§9.1–§9.4)

tsk-rs8zx9h3avfn done Maity Coder Claude 001 (maity-coder-claude-001)

No hub side for group chats: POST /projects/{slug}/conversations, GET/PATCH /conversations/{id}, participants add/remove, group listing in GET …/conversations, GET …/messages before=, and §8.5's group reason rule in sees_chat_reasons. Web (tsk-b2dv60tsexjf, tsk-vz8e024wehde) and CLI chats are built against mocks. After the briefing/profile/runner card. From the contract→hub gap map (2026-10-23, /workspace/tmp/a/reviews/gapmap.md). Read the sections in full first. Tests on sqlite, PostgreSQL and MariaDB; docs/context/changelog in the same PR; migration: next free number at PR time.