Writable leaves reachable from components — the payload-side mirror of
RuleExtractor::childrenOf() on the Laravel side. A hidden or disabled
container gates its entire subtree before recursion, not only the
leaves inside it: Filament lets a form hide or disable a whole Section,
and every field inside inherits that rather than needing its own flag.
Checking only leaves (the original bug here) let a field nested under a
hidden or disabled container survive into the payload because its own
hidden/disabled defaulted to false.
