Attempt to persist text input state across the platform on beforeunload (#9612)

Signed-off-by: Victor Ilyushchenko <alt13ri@gmail.com>

packages/ui/src/components/internal/Root.svelte

@@ -41,12 +41,23 @@
   function handleWindowBlur (): void {
     updateAppFocused(false)
   }
+  function handleWindowBeforeUnload (): void {
+    // Many text inputs across the platform rely on the blur event to persist state,
+    // but they don’t account for cases where the tab is forcefully closed, navigated away from, or destroyed.
+    // Handling beforeunload for every input individually is impractical,
+    // so leveraging existing blur behavior is a more maintainable approach.
+    // While not foolproof—since most blur handlers are async and may not complete in time, it’s sufficient for most cases.
+    // A more robust solution, such as tracking pending async mutations to block tab unload,
+    // would require significant reworks across the board.
+    ;(document.activeElement as HTMLElement)?.blur?.()
+  }
 
   onMount(() => {
     document.addEventListener('visibilitychange', visibilityChangeHandler)
     window.addEventListener('wheel', handleWindowFocus)
     window.addEventListener('focus', handleWindowFocus)
     window.addEventListener('blur', handleWindowBlur)
+    window.addEventListener('beforeunload', handleWindowBeforeUnload)
   })
 
   onDestroy(() => {
@@ -54,6 +65,7 @@
     window.removeEventListener('wheel', handleWindowFocus)
     window.removeEventListener('focus', handleWindowFocus)
     window.removeEventListener('blur', handleWindowBlur)
+    window.removeEventListener('beforeunload', handleWindowBeforeUnload)
   })
 
   onDestroy(