payloadExtraction: true + ssr: false + cloudflare-pages preset → _payload.json URLs serve text/html instead of application/json.

Live repro: https://nuxthub-839.pages.dev

curl -I https://nuxthub-839.pages.dev/_payload.json
# content-type: text/html;charset=utf-8  ← wrong

curl -I https://nuxthub-839.pages.dev/about/_payload.json
# content-type: text/html;charset=utf-8  ← wrong

No _payload.json files are generated during build, so CF Pages serves the SPA fallback HTML.