Docs: API_REFERENCE + ARCHITECTURE updated to the owner-chosen
email-match association model (incl. anonymous, tradeoff documented) and
listMemberSubmissions; HANDOFF pass-32; corrected pass-31 header.
Landing: tightened the <=600px breakpoint (nav/section/card padding) and
added a <=400px block so the nav fits ~320px without overflow. CSS-only
inside media queries; desktop unchanged.