Update long spec field from subitem detail changes

Subitem product and footing fields are scattered, causing inconsistent build specs. Consolidate those inputs into one item spec so crews and managers get correct instructions same day.

Overview

Uncontrolled subitem edits leave build specs fragmented and crews working from different instructions. This flow consolidates subitem detail into a single, human-readable spec on the item so supervisors and crews have accurate instructions and can move forward same day.