Product surface

Piece	Role
/config/design-system	Only workspace (Appearance + Live Preview)
design-system/+page.svelte	Tabs: overrides, preview, themes, presets, layout, style, …
design-system-preview.svelte	Live Preview component catalog
appearance-api.ts	Theme CRUD + prefs via fetchApi (CSRF)
/user Settings	Quick density/variant strip + link to ?tab=overrides

Theme activation/creation/deletion lives only here. The dashboard no longer hosts a workspace/theme picker (WelcomeThemePicker removed), and /config/extensions no longer has a Themes tab (its ThemesView was a broken duplicate that POSTed { themeName } to /api/theme/update-theme, which expects { themeId, customCss }). /config/system-settings?group=appearance is retitled Seasonal Effects — it only controls seasonal login decorations, not themes.

Control → test matrix

Control	Unit	E2E
User prefs save/clear/reload	appearance-api	✅ appearance.spec
Themes tab shell	—	✅ appearance-golden
Golden create→list→delete	appearance-api	✅ appearance-golden
Live Preview tab	—	✅ design-system.spec
Surface → --admin-bg-card	theme-preset-mapper	unit

Run

bun run test:unit -- tests/unit/config/appearance-api.test.ts tests/unit/theme-preset-mapper.test.ts
bun x playwright test tests/e2e/routes/config/design-system.spec.ts tests/e2e/routes/config/appearance.spec.ts tests/e2e/routes/config/appearance-golden.spec.ts