Resolve URL shorteners and prompt for ambiguous description links

Tapping bit.ly/tinyurl/t.co/etc. in a description or comment previously
opened Safari even when the destination was a playable YouTube URL.
Added an opt-in "Resolve Short Links" toggle under YouTube Enhancements
(off by default) that follows the redirect on tap: if the target is a
YouTube/PeerTube/direct-media URL, open it in-app; otherwise prompt the
user before falling back to yt-dlp extraction or the browser.

Also added a confirmation dialog for non-shortener links that only
matched the loose .externalVideo yt-dlp fallback, so arbitrary web
pages in descriptions no longer silently kick off extraction.

Prompts live on NavigationCoordinator and are dual-hosted by YatteeApp
and ExpandedPlayerSheet so they remain visible whether or not the
expanded player is covering the main view.

Yattee/YatteeApp.swift

@@ -51,6 +51,9 @@ struct YatteeApp: App {
     #endif
     @State private var showingOpenLinkSheet = false
 
+    // Ambiguous-link prompts are stored on NavigationCoordinator so they can
+    // be dual-hosted by the root app view (here) and the expanded player sheet.
+
     init() {
         // Configure Nuke image loading pipeline
         ImageLoadingService.shared.configure()
@@ -192,6 +195,23 @@ struct YatteeApp: App {
                         handleDescriptionLink(url)
                     }
                 }
+                .onReceive(NotificationCenter.default.publisher(for: .promptResolvedShortLink)) { notification in
+                    if let url = notification.object as? URL {
+                        appEnvironment.navigationCoordinator.resolvedShortLinkPrompt = url
+                    }
+                }
+                .onReceive(NotificationCenter.default.publisher(for: .promptAmbiguousExternalLink)) { notification in
+                    if let url = notification.object as? URL {
+                        appEnvironment.navigationCoordinator.ambiguousExternalLinkPrompt = url
+                    }
+                }
+                // Present confirmation dialogs at root level only when the expanded
+                // player isn't covering it. ExpandedPlayerSheet hosts the same
+                // dialogs when it *is* expanded, so they always sit on top.
+                .resolvedLinkPrompts(
+                    shouldHost: !appEnvironment.navigationCoordinator.isPlayerExpanded,
+                    appEnvironment: appEnvironment
+                )
         }
         #if os(macOS)
         .windowStyle(.hiddenTitleBar)