Write translations for one language of a poll. Only the given language is touched — other languages are never modified. By default the provided translations are deep-merged into the language's existing layer (send only what changed; set a key to null to delete it). Set replace: true to swap the language's entire layer, or remove: true to delete the language.

The translations object mixes two kinds of keys: slide _id keys mapping to an object translating that slide's content (title, subtitle, copy, disclaimer, leftLabel, rightLabel, placeholder, consentLabel, rewardBanner, rewardCode, customCTA, customRewardBanner as strings; answers, rows, actions, actionUrls as objects keyed by handle — never arrays; formInputs as an array aligned by index with the slide's form inputs), and widget CTA keys (next, submit, ...) mapping to translated strings. Use language default (CTA keys only) to override widget chrome in the survey's own language. Keys and handles are validated against the poll's actual slides.