Add annotation for pagy

[mokevnin]

Type of Change

• Add RBI for a new gem
• Modify RBI for an existing gem
• Other:

Changes

• Gem name: pagy
• Gem version: 43.6.2
• Gem source: https://github.com/ddnexus/pagy/blob/e85430530be38b76d4329c2fea7d870dee60e94f/gem/lib/pagy/toolbox/paginators/method.rb#L21
• Gem API doc: https://ddnexus.github.io/pagy/docs/api/paginators/
• Tapioca version: 0.19.1
• Sorbet version: 0.6.13164

Annotates a single method, Pagy::Method#pagy — the entry point users include into
their controllers/views.

It is defined with define_method inside an anonymous Module.new, so tapioca's runtime
reflection picks up its arity and protected visibility but emits no signature.

• paginator is Symbol: it is used only as a key into the frozen paginator lookup hash
  in method.rb, so anything else raises.
• collection and options are T.untyped: they are forwarded verbatim to whichever
  paginator is selected, and each accepts a different kind of collection (AR relation,
  Array, Pagy::Search::Arguments, …).
• The return is deliberately T.untyped rather than a tuple, because it varies by
  paginator: [Pagy, records] for the offset/countless/countish/keyset family,
  [Pagy::Calendar, Pagy, records] for :calendar, and a bare Pagy object for the
  search paginators in passive mode. A tuple type would be wrong for those callers, and
  Sorbet cannot discriminate on the symbol literal to overload them apart. The comment
  above the sig documents the three shapes instead.

bundle exec repo check --gem --ref origin/main passes locally (index, rubocop, rubygems,
runtime, static).