Document the run import API

The REST API reference now covers run import, and every import format has a quick-reference spec at a glance.

• Added reference pages for the import and batch import endpoints.
• Added a spec block to each format page (OpenHTF, WATS, ATML, TestStand, STDF, ATDF, CSV, Excel) showing encoding, extension, detection, origin, and what it maps to.
• Replaced the import endpoints table with cards matching the rest of the page.