docs: define streaming mcp architecture

docs/database-schema.md

@@ -49,6 +49,8 @@
 - `agent_operation_bindings`
 - `published_agents`
 - `platform_api_keys`
+- `stream_sessions`
+- `async_jobs`
 - `invocation_logs`
 - `usage_rollups`
 - `yaml_import_jobs`
@@ -180,6 +182,46 @@
 
 - `unique (workspace_id, name)`
 
+### `stream_sessions`
+
+- `id`
+- `workspace_id`
+- `agent_id`
+- `operation_id`
+- `mode`
+- `status`
+- `cursor_json`
+- `state_json`
+- `expires_at`
+- `last_poll_at`
+- `created_at`
+- `closed_at`
+
+Индексы:
+
+- `(workspace_id, status, expires_at)`
+- `(operation_id, status)`
+
+### `async_jobs`
+
+- `id`
+- `workspace_id`
+- `agent_id`
+- `operation_id`
+- `status`
+- `progress_json`
+- `result_json`
+- `error_json`
+- `expires_at`
+- `created_at`
+- `updated_at`
+- `finished_at`
+
+Индексы:
+
+- `(workspace_id, status, expires_at)`
+- `(operation_id, status)`
+
 ## 7. Workspaces and access layer
 
 ### `workspaces`