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-viewer/SWViewerHeader.tsx

@@ -1,4 +1,5 @@
 import { forwardRef, useId, useLayoutEffect, useRef, useState, type ButtonHTMLAttributes, type HTMLAttributes, type KeyboardEvent, type ReactNode } from "react"
+import { moveRovingFocus } from "../shared/roving-focus"
 import { SWViewerMenu } from "./SWViewerMenu"
 import { SWViewerSwitch } from "./SWViewerControls"
 import { SWViewerIcon } from "./SWViewerIcon"
@@ -111,15 +112,7 @@ function MenuButton({ item, iconOnly, onCommand }: { item: Extract<SWViewerHeade
 function Tabs({ item, onCommand }: { item: Extract<SWViewerHeaderItem, { type: "tabs" }>; onCommand: (c: SWViewerCommand) => void }) {
   const select = (value: string) => { item.onValueChange?.(value); onCommand({ id: item.id, itemId: item.id, value }) }
   const onKeyDown = (event: KeyboardEvent<HTMLDivElement>) => {
-    const keys = ["ArrowRight", "ArrowLeft", "ArrowDown", "ArrowUp", "Home", "End"]
-    if (!keys.includes(event.key)) return
-    const buttons = Array.from(event.currentTarget.querySelectorAll<HTMLButtonElement>('[role="radio"]:not(:disabled)'))
-    const index = buttons.indexOf(document.activeElement as HTMLButtonElement)
-    if (index < 0) return
-    event.preventDefault()
-    const next = event.key === "Home" ? 0 : event.key === "End" ? buttons.length - 1 : (index + (event.key === "ArrowRight" || event.key === "ArrowDown" ? 1 : -1) + buttons.length) % buttons.length
-    buttons[next].focus()
-    buttons[next].click()
+    moveRovingFocus(event, Array.from(event.currentTarget.querySelectorAll<HTMLButtonElement>('[role="radio"]:not(:disabled)')), { vertical: true, select: true })
   }
   const current = item.options.some(option => option.value === item.value) ? item.value : item.options.find(option => !option.disabled)?.value
   return (