Archon adds Pi to coding workflow

This is less a model launch than a workflow composition story: Archon is making agent choice modular, with Pi handling planning and review handoff while Claude does the implementation work.

• –The workflow cleanly splits clarify, plan, implement, and validate, which is the right shape for reducing drift on larger coding tasks.
• –Pi’s role is intentionally narrow: generate the plan, submit it through plannotator’s HTTP approval UI, and iterate until a human signs off.
• –Supporting Claude, Codex, and Pi in one harness lowers switching costs for teams that already have model preferences.
• –The review gate matters more than the agent swap: human approval before implementation is where many coding-agent workflows break down.
• –Because Archon is open source and YAML-driven, this looks reusable rather than one-off demoware.