PtcRunner.SubAgent.Loop.TextMode (PtcRunner v0.9.0)

Unified execution loop for text output mode.

Text mode auto-detects the appropriate behavior from two signals:

Tools?	Return type	Behavior
No	`:string` or none	Raw text response (single LLM call)
No	complex type	JSON response (validated against signature)
Yes	`:string` or none	Tool loop → text answer
Yes	complex type	Tool loop → JSON answer

This module replaces the former JsonMode and ToolCallingMode.

Summary

Generate a preview of the text mode prompts.

Execute a SubAgent in text mode.

@spec preview_prompt(PtcRunner.SubAgent.t(), map()) :: %{
  system: String.t(),
  user: String.t(),
  tool_schemas: [map()],
  schema: map() | nil
}

Generate a preview of the text mode prompts.

Returns the system and user messages that would be sent to the LLM, plus tool schemas and JSON schema when applicable.

@spec run(PtcRunner.SubAgent.t(), term(), map()) ::
  {:ok, PtcRunner.Step.t()} | {:error, PtcRunner.Step.t()}

Execute a SubAgent in text mode.

Auto-detects the variant based on tools and return type, then dispatches to the appropriate execution path.