The 8x6nki / szm8ld share-id gates stay explicit. New coverage:
available-language reporting, requested-language fetch with the
untranslated banner flag, prod filtering still keyed on NODE_ENV, and
the language-nav banner/switcher data. The both-languages path runs on
a synthetic _fixture-bilingual post (removed after the suite) — real
posts are single-language by design.
