class ToolResultLoop

Re-invokes the inner stack whenever the last message is a :tool result.

After the inner pipeline runs (LLMCall responds, ToolCall executes tools and appends :tool messages), this middleware checks if tool results are pending. If so, it increments the iteration counter and loops — sending the tool results back through MaxIterations → ToolCall → LLMCall so the LLM can see them.

The loop breaks when:

• The LLM responds with text only (no tool calls) — last message is :assistant
• env[:should_exit] is set (e.g. by MaxIterations)