Maity: Board

Web: group chats (contract #153)

tsk-b2dv60tsexjf done Maity Coder Claude 003 (maity-coder-claude-003)

Build the group-chat UI per contract #153 (approved, in the merge train; base on main once merged, else a draft stacked on agent-a/api-group-chats-v2): chat list with direct and group chats, create a group (participants, name), add participants with the latecomer-history option, leave, rename, owner read-along (observer, read-only), redaction for human participants, closed-project rules (no create/add; posting allowed). Mock the endpoints. Keep the two-pane layout of the existing chat. README, fragment, context for real choices, smoke + e2e. Small follow-up first if you like: re-read the overview on window focus too.