PR #3410 - ReviewStage/luke

D32 of the design-system migration (Desktop stack, base feature/desktop-d30-plan-template-editor, #3409; D31 has no PR, it is covered by D82).

What

Settings › Experimental (apps/desktop/src/renderer/settings/experimental-page.tsx) moves onto @luke/ui:

Each experiment's card is SettingsSection, replacing the desktop's SettingsGroup.
The signed-out note is the caption Text in the subtle tone, replacing a .settings-note paragraph.

These parts were already on the design system and are unchanged:

the switch rows (SwitchRow over SettingsRow/Switch)
Video calls' Avatar row (the shared schema rows from F40)
the empty state (EmptyState)

Send feedback stays an inline press among the row's description words. The barrel has no inline-link button, and a quiet Button there would be a redesign. Its .settings-detail-act rule is shared with Coding agents' Fast access link.

No caller here imported @luke/ui/compat. No selector became unused: SettingsGroup, .settings-card and .settings-note still have other callers.

Visible changes

None. At 1280×840 the before and after captures match pixel for pixel in both themes, for the populated page and the signed-out note.

Tests

experimental-page.test.ts keeps all six behaviour tests: the switch writes, Send feedback per experiment, the empty state, the signed-out note, and Video calls' avatar showing and hiding. The one change is in "Video calls off": it counted cards by the retired .settings-card class and now counts the cards' sections.
pnpm check:affected exits 0.

Evidence

Captured on Linux with headless Chrome at 1280×840, using #3405's method. A throwaway, uncommitted test rendered the real ExperimentalPage inside SettingsPage, with Video calls and Factory on. That markup was framed with the built desktop stylesheet.