letsdo — a local agent worker for Backlog.md/markdown tasks. OOP structure: Letsdo::PromptStore (agents/), Letsdo::OutputStreamer and Letsdo::PiRunner (pi --mode json), Letsdo::Agent (one run), Letsdo::Loop (orchestrator loop), Letsdo::CLI. Minitest tests. Will later be split into a separate repository.