- Every dropdown-style value-picker trigger takes its chrome from `dropdownTriggerVariants` in `packages/ui/src/components/ui/dropdown-trigger.ts`; call sites add layout classes only. Deliberately chrome-less pickers in composers or headers are the exception.
Load every matching reference before editing. User-facing or accessible text must load `locale-ui-patterns`. Settings composition is owned by `settings-ui-patterns`, which declares `theme-system` as its one-way companion.
- Menus, selects, and autocomplete pickers with ArrowDown/ArrowUp navigation must also support Ctrl+N/Ctrl+P, including submenus and searchable lists.
- Keep this behavior in shared components so callers inherit it. Use the keyboard mapping in `packages/ui/src/components/ui/dropdown-navigation.ts`; feature code must not duplicate key detection.
- Lists that own their active option or stop keyboard propagation must call the shared navigation helper at their own event boundary. Wrapping a custom list in a dropdown does not guarantee that its navigation events reach the wrapper.
- Route both key pairs through the same selection logic, preserving disabled-item skipping, boundary or wrap behavior, highlight, and scroll visibility. Consume each navigation event once, only while the menu or picker is active; preserve IME text entry and other modifier chords.
- Verify Ctrl+N/P alongside arrow keys in the real component, including search-input focus, submenus, and closed state. A key-mapping unit test alone does not verify event propagation or focus behavior.
Use `IconName` for icon values stored in arrays, objects, state, or config. `Icon` has no `size` prop. Run `bun run icons:generate` when introducing a sprite name, and never edit `sprite.ts` manually. Load `references/icons.md` for the complete workflow.
Animate only `transform` and `opacity`. Use `transform: rotate(...)`, not the individual `rotate` property. Non-composited properties recalculate style continuously; geometry also triggers layout, and wrappers, `will-change`, `contain`, or stepped timing do not remove that cost. Animate only while conveying live information.
For any other technique, load `performance-engineering` and `scripts/perf/DOCUMENTATION.md`, measure it with `bun run profile:animation`, and add a fixture variant when needed. This skill owns animation styling; `performance-engineering` owns performance evidence.