A category whose PL24 drill/parts fetch errors (e.g. a broken catalog snapshot
returning HTTP 500) was indistinguishable from a genuinely empty leaf — both
came back with empty parts, so the UI showed a misleading "no parts found".
getCategoryWithParts now: (1) for a pl24 group node (link_wid marks a groups
table) with no children, drills via getChildren — returns the subgroups if PL24
serves them, otherwise flags loadError (these group nodes are never legitimately
empty); (2) sets loadError when the leaf parts fetch throws. loadError is only
true when the lists are actually empty, so genuine empty leaves stay clean.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>