The ui-new/*.h screens are header fragments compiled only as part of
UITask.cpp, in include order. Two implicit rules a contributor can trip on:
include order (a static inline helper / shared scratch is visible only to
later fragments) and single-TU-only (some fragments define external-linkage
symbols at file scope, e.g. NearbyScreen::FILTER_LABELS, so reusing one from a
second .cpp is a duplicate-symbol link error).
Spell both out in a contract comment at the inclusion block, and raise the
single-TU note to a callout in the framework guide. Comments only.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>