create_goal_criteria_fallback_agent

Create the goal-only fallback agent for criteria generation.

This agent has no context tools, repository access, or HITL: it drafts acceptance criteria from the goal message alone. GoalCriteriaMiddleware invokes it when the context-enabled agent fails at the graph level (e.g. exhausts its recursion budget) or returns no usable proposal, restoring the guarantee that /goal always yields criteria unless the model itself is unavailable.