33da2e5073
Reviewer caught a stale comment: it claimed the root-`v-if` fragment's `$el` "resolves to the real host node". It doesn't — `$el` is the fragment boundary anchor; measureElement/useBoxMetrics resolve a Box ref by drilling the component subTree to its first host node. Also fixed a leftover `box.ts` reference (now box-validate.ts). Comment-only; code was correct. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>