harden

<!-- HARNESS MIRROR — do not edit here. Canonical source: skills/ or commands/. After editing source, copy into cli/assets/<harness>/ and repo-root harness mirrors. --> **Context:** this sub-skill is one lens of the broader `ui-craft` skill. If the `ui-craft` skill is also installed, read its SKILL.md first for Discovery + Anti-Slop + Craft Test, then apply the specific lens below. Harden the UI at `$ARGUMENTS` for production. Load the `ui-craft` skill. **Coverage matrix — check every key surface:** 1. **Loading** — skeletons match the final layout (no CLS on resolve), shown after ~200ms to avoid flash on fast responses. Never a generic centered spinner when a skeleton is possible. 2. **Empty** — purposeful: one line explaining why it's empty + one clear primary action. Illustration optional, CTA mandatory. 3. **Error** — inline, actionable. "Save failed. Try again / Copy error / Contact support" — never just "Something went wrong." Surface the *what* and the *next step*. 4. **Partial data** — `—` (em dash) for missing metrics, never `N/A` or `null` or `0` when the value is truly unknown. 5. **Long content** — truncation with `title` tooltip, `text-overflow: ellipsis`, container queries for constrained regions. Test with a 120-character name. 6. **i18n** — no hardcoded strings, ~1.3× text expansion slack for German, narrower glyphs for CJK, RTL flip consideration for icons with direction. 7. **Offline / slow** — optimistic UI with reconciliation on failure; skeleton persi...