Slice: DFG-4 deterministic previews and renderer orchestration
Goal: Produce bounded, reproducible previews and configured derived outputs from validated project data without granting arbitrary execution or canonical write authority.
In scope: Preview contracts, renderer declarations, input and output confinement, deterministic render identity, stale detection, atomic derived output replacement, render status, MCP preview and render-status tools, and tests.
Out of scope: Canonical changeset application, arbitrary commands, project-specific adapters, Git mutation, deployment, accounts, HTTP transport, and a web UI.
Done when: The same validated project and renderer version produce the same preview identity; stale or escaped inputs fail closed; failed renders preserve prior derived output; the MCP surface cannot select an undeclared renderer or command.
Owners: Canonical files retain facts. Changesets retain proposals. Preview and renderer owners produce disposable derived artifacts only.
