fix(lint): see the grouped gsap.set that stages a whole scene at once (#3737)

Hiding several elements in one call is the shortest way to stage a scene, and it was
the one form the hidden-selector extractor could not read: a multi-element array
failed the target regex, which forbade commas, and a single-element array then failed
the selector parse, which accepted only a quoted string or a known alias. So the two
error rules that ask whether a hidden element is ever properly revealed had an empty
hidden set for every grouped hide.

Each part of a group now resolves on its own, and a comma-separated selector string
resolves the same way. The target pattern stays paren-free so a set whose vars are a
variable cannot run past its own closing paren and swallow the next call.

Two false positives the wider hidden set exposed in the fullscreen-overlay rule: a
fromTo at 0 seats its from-vars immediately, so hidden from-vars there mean the
overlay does start hidden; and an overlay hidden by a standalone gsap.set is what
that rule's own fixHint prescribes.