fix(extract): capture arrow methods returned from JS/TS factory functions

walk_defs stopped descending into a function body once the function itself
was extracted, so arrow methods of an object literal returned from a factory
(the Zustand actions-slice pattern) were never visited. Let JS/TS/TSX descend
into function bodies (as Wolfram already did) and resolve an arrow's name from
a 'pair' parent's key, so { addItem: (...) => {...} } is captured as a Function.
Anonymous nested arrows have no resolvable name and are skipped, so no noise.

Closes #341