feat(sw): viewer layer popup bulb icon and all-layers switch

User-approved 2026-10-22 change to the SW Viewer layer popup.
- New public export SWLayerVisibilityIcon({ on }) + SWLayerVisibilityIconProps:
  the SW Header layer bulb art reused as is (header design and behavior unchanged).
- Layer rows: eye (Eye / EyeOff) icon replaced by the bulb, 24 x 24 button kept.
- All layers: the 전체 켜기 / 전체 끄기 buttons replaced by one SWViewerField +
  SWViewerSwitch on top. ON only when every layer is shown; a partial state reads
  OFF and a click shows all. Derived from the hidden-layer state, so it stays synced.
- AI docs (VIEWER.md 4.1, catalog, design rules, composition, AI_GUIDE sync) and
  example H follow the new rule, replacing the 2026-10-21 eye-icon rule.
- viewer.browser.mjs: layer popup checks moved to the bulb / switch behavior.

packages/sw/src/components/sw-viewer/index.ts

@@ -7,4 +7,6 @@ export {
   type SWViewerSectionProps, type SWViewerFieldProps, type SWViewerSwitchProps, type SWViewerSliderProps, type SWViewerInputProps,
   type SWViewerButtonProps, type SWViewerBadgeProps, type SWViewerStatusProps, type SWViewerStatusState,
 } from "./SWViewerControls"
+// Layer popup visibility (2026-10-22): the SW header layer bulb art, reused as is.
+export { SWLayerVisibilityIcon, type SWLayerVisibilityIconProps } from "../sw-header/components/SWHeaderLayerIcons"
 export type { SWViewerHeaderItem, SWViewerHeaderGroup, SWViewerMenuEntry, SWViewerCommand } from "./types"