Variant A v3 — one responsive design
The v2 shell, populated with ONLY features that ship today (audited against main/prod). Real-but-omitted added back: clarify-before-run cards, the customize-columns modal, the SQL-explainer bullets, follow-up chips, feedback bar, the flag-gated federation banner, the ✦ trace chip. Invented features removed: assumptions are display-only (no "Re-run with changes"), no AI warning, Export is CSV only. ONE responsive file — resize to see desktop↔mobile.