PS.6 Download for 3D printing on a Library item page

Spec: docs/0.9-PRINT-STAGE.md. For people who keep their own slicer: a size or bed choice on the item page gives a 3MF or STL, with an honest print-ready line per item. Server side beside tools/library/variant-export.mjs. Secondary to the print stage. Export tool tools/printstage/print-export.mjs (STL and 3MF scaled to the bed, with an honest print-ready line) and the item-page form are built and tested (test-export 6/0); the handler is not installed.

mounts-09 2026-11-06: print-file.php installed (public_html/library/print-file.php + the rewrite line in .htaccess). Lab testers and staff only; anonymous gets 404. Real item page (Griddle, 48 in): the form shows and the STL downloads; curl as a lab session: STL 684 bytes, 3MF a valid zip; nothing is kept.