Phase 4.4 — demo/rest/checkout-redirect/ (server-only)

[drewangell]

Plan file: docs/v4-plans/phase-4/04-demo-rest-checkout-redirect.md

PRD: docs/PRD.md

This issue tracks execution of the plan file above. The plan file is the source of truth for scope, acceptance criteria, and verification — pick this issue up when ready to take the iteration, execute against the plan, and close when the acceptance criteria are met.

Phase 4 — Templates / Samples / Demos / Helper

Links above are relative paths. They resolve on main after PR #285 merges (the PR adds both the revised PRD and the docs/v4-plans/ tree).