complete-exporter-setup

# Exporter completeness checklist Before finalizing an exporter implementation: 1. **Registry entry** — Ensure `shop/plugins/registry.py` includes the new exporter class registration 2. **Implementation** — Write the exporter class in `shop/plugins/<format>_export.py` with correct format handling 3. **Documentation** — Add a row to `docs/exporters.md` with format name, module name, and description 4. **Golden test file** — Run `make golden` to generate and commit `tests/golden/order.<ext>` for the new format All four must be completed together. Missing any one will fail the CI lint check.