Update many annotation tasks in one request, operating in one of two mutually exclusive modes.

In ids mode, provide a list of task IDs together with an assigned_to and/or a status (limited to pending_redo or completed) to apply those field changes to each listed task; only tasks that currently exist are affected and IDs that do not resolve are silently skipped. In audit_assignment mode, provide an evaluation ID, queue ID, and evaluation item IDs to assign Level 1 and/or Level 2 auditors for those items, creating the underlying audit tasks when they do not yet exist; a Level 2 auditor cannot be assigned unless a Level 1 auditor is already present. Exactly one of ids or audit_assignment must be supplied, and assigned_to/status are only valid in ids mode. Access and state checks run before any write, so the request is rejected as a whole with nothing persisted if any task is inaccessible, if a status change is attempted without a modification role, or if an already-completed task would be reassigned; audit assignment also requires a modification role. Reassigning a task to a new user emits a task-start lineage event, and the response returns the affected annotation tasks.