Engine architecture

/implement is two steps: derive a contract from the task text, then deliver one bounded change.

• derive parses and validates the contract, with the record's budget carried verbatim.
• deliver runs one fresh Pi subprocess — every guard loaded — in its own linked Git worktree, commits a candidate, validates it, and writes a receipt.
• Worktree isolation keeps ordinary writes off the caller's checkout; it is isolation from the caller's files, not a security sandbox.

The pieces are the TypeScript adapter that exposes /implement inside Pi, and the Python core that does the work. Terms are in the engine glossary; the product is described on About Satyrn Engine.

Describes the engine synced at 9aecfb513be3211d5f5753bf778807ccecfd76ca.