- _get_level_hashes: remove (0x1F << parent_shift) from range_end so
bitmap only includes children of the actual parent prefix (not all
parents). Add level 0 virtual root that queries all level-1 entries.
- merkle_sync_start: send HASHES at level 0 (virtual root) instead of
level 1/prefix 0. Root-level REQUEST prefix reconstruction now uses
the correct level-1 prefix from DB.
- _handle_batch: use merkle_sync_prefix_bytes(next_lvl) for synthetic
child HASHES instead of current level's pb_i (could be wrong size).
- Remove timeout/retry mechanism: delete _session_timeout_cb,
_session_start_timer, timer/retries fields. ETCP provides reliable
transport — no need for application-layer retries.
- Remove is_dm column from channels table (dm detection by member count)
- Rename member name column to userinfo — extensible json_flat format
- Add json_flat.c/h library for compact JSON serialization
- Fix join_sig message format: use ch_x25519+ch_ed25519 instead of channel_id string
- Remove name from join_msg body (now in userinfo via json_flat)
- Update chat_core, chat_sync, member_sync, db_manager to new format
- Add topo_strategy.txt — архитектурные заметки по топологии
Replace etcp_router_bind/etcp_route_send/etcp_router_unbind with
direct etcp_bind/etcp_send/etcp_unbind + find-conn-by-node_id helpers.
Same approach as db_sync (0x20). Service IDs unchanged (0x30, 0x31).
Evgeny