refactor(sw): share roving focus and outside pointer handling

- components/shared/roving-focus.ts (moveRovingFocus): the same Arrow / Home / End algorithm of SWFooter, SWToolGroup,
  the SWViewerHeader tabs and SWHomeMenu; each caller passes its own keys, wrap and select behavior.
- components/shared/use-outside-pointer.ts (useOutsidePointerDown): the same pointerdown effect of the SWHeader
  dropdowns, layer menu, document title and More. Escape, focus return and positioning stay in each component.
Both modules are internal: the package entry and the public declarations are unchanged.

packages/sw/src/components/sw-home-menu/SWHomeMenu.tsx

@@ -3,6 +3,7 @@ import {
   type ButtonHTMLAttributes, type CSSProperties, type KeyboardEvent, type MouseEvent, type ReactNode,
 } from "react"
 import { useSWPopupStack } from "../sw-header/components/SWHeaderPropertyPanel"
+import { moveRovingFocus } from "../shared/roving-focus"
 import titleBadge from "./assets/title-badge.svg"
 // Imported where the component is used (not only in index.ts) so bundlers keep it with sideEffects: ["**/*.css"].
 import "../../theme/sw-home-menu.css"
@@ -354,14 +355,7 @@ export const SWHomeMenu = forwardRef<HTMLDivElement, SWHomeMenuProps>(function S
       else rows[Math.min(rows.length - 1, Math.max(0, index + (event.key === "ArrowDown" ? 1 : -1)))]?.focus()
       return
     }
-    if (!["ArrowLeft", "ArrowRight", "Home", "End"].includes(event.key)) return
-    const items = focusableItems(rootRef.current)
-    const index = items.indexOf(document.activeElement as HTMLElement)
-    if (index < 0) return
-    event.preventDefault()
-    const next = event.key === "Home" ? 0 : event.key === "End" ? items.length - 1
-      : (index + (event.key === "ArrowRight" ? 1 : -1) + items.length) % items.length
-    items[next].focus()
+    if (["ArrowLeft", "ArrowRight", "Home", "End"].includes(event.key)) moveRovingFocus(event, focusableItems(rootRef.current))
   }
 
   const resolvedAccent = accent === "auto" ? (openPanelId ? "outline" : "sections") : accent