Back closes what is open

On a phone the Back button left the page under an open menu, sheet or dialog. An open overlay now says so (new
IDOverlayHost, cascaded by MainLayout; OverlayService keeps them newest last): DModal and DDropdown through the
cascade, so the D components stay free of app services, and the nav menu, PhoneSheet and the full-screen globe through
the service. MainLayout's location-changing handler lets Back close the newest overlay instead of leaving the page; a
link followed or the app's own navigation (signing out after its question, say) closes them all and goes on. Blazor
can't tell Back from the app's navigation, so a capture-phase popstate listener in main.js marks Back
(AppStatusService.TookBack). No history entries are pushed. Phone flow: Back closes the menu, a card's More sheet, the
composer and the full-screen globe one after another without leaving the feed, and with nothing open goes back.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

wwwroot/main.js

@@ -140,6 +140,16 @@ document.addEventListener("click", event => {
 		window.logFromJs(e.message, "openThread")
 	}
 })
+// The Back button (a popstate) as opposed to the app's own navigation: Blazor's location-changing handlers can't tell
+// them apart, and MainLayout lets Back close an open overlay but lets the app's navigation through. Registered for the
+// capture phase, so it runs before Blazor's own listener.
+let backAt = 0
+window.addEventListener("popstate", () => backAt = Date.now(), { capture: true })
+window.tookBack = () => {
+	const back = Date.now() - backAt < 1000
+	backAt = 0
+	return back
+}
 window.canHover = () => {
 	try {
 		return window.matchMedia("(hover: hover)").matches