The participant sync and the non-member prune now remove only ogólny's
rows. A user taken out of studenci, even briefly, keeps their DMs (the
live membership check denies access while they are out) and gets them
back when re-added, instead of losing them for good.
GET /_bm/api/v1/chat gives a chat-group member ogólny (the bm/1 group
conversation, adopted once as the system default channel under an
advisory lock), its unread and mention counts, the member's DMs newest
message first, the moderator flag and the composer limits. Every member
bootstrap syncs participants with the group: missing members join
ogólny, users no longer in the group lose their rows in every bm/1
conversation. A non-member gets only member:false and is pruned.
GET /_bm/api/v1/chat/members lists members (id, name, surname, handle,
is_bot from golem15.chatbots when active) and assigns missing handles;
non-members get 404.
The chatchannels access policy (ChatAccess) is installed from a
database hook: bm/1 for members only, nobody manages channels.
bm:chat-sync creates the groups when missing, syncs and assigns
handles. Migration 20261026130000_seed_jz_bm_chat_groups creates
studenci and moderatorzy without members; its rollback keeps them.
