Multiple spending paths

📝 Draft. This chapter has not been reviewed yet — content may be incomplete or change.

Problem. Build a covenant that can be spent in more than one way — e.g. a cooperative path and a cancel/timeout path — and select between them at spend time.

🚧 This recipe is a stub. Outline of what it will cover:

• A Simplicity program with Either<(), ()> paths (PATH::LEFT / PATH::RIGHT).
• Selecting a path with a simplicityhl witness: Left(()) vs Right(()).
• Worked example: the lending pre_lock covenant — SetupLending takes the left path; CancelOffer takes the right path with a borrower signature.
• Using required_index on inputs so the covenant's introspection lines up.
• Cooperative vs unilateral paths, and how they show up in lifecycle.

See the pre_lock discussion in the lending walkthrough in the meantime.