Fix timed links resuming at watch position instead of URL timestamp

Timed links arrive wrapped as yattee://open?url=... from the share
extension, but the timestamp was parsed from the wrapper URL, where a
single-? form like youtu.be/ID?t=N hides t inside the url query item.
With no startTime the player fell back to saved watch progress.

- Add URLRouter.unwrapped(_:) resolving the wrapper to the inner URL
  (raw remainder after ?url=, since the share extension does not encode
  & and URLComponents would drop &t= parts) and use it in handleDeepLink
- Thread forceStartTime through openVideo/playPreferringDownloaded/play
  so explicit link timestamps beat the 90%-watched restart threshold,
  clamped to just before the end; resume flows keep the old behavior
- Carry the parsed timestamp through OpenLinkSheet's play action, which
  dropped it entirely
- Cover timestamp parsing and wrapper unwrapping in NavigationTests

Yattee/YatteeApp.swift

@@ -500,6 +500,9 @@ struct YatteeApp: App {
     /// Handle incoming deep link URLs.
     private func handleDeepLink(_ url: URL) {
         let router = URLRouter()
+        // Resolve yattee://open?url=… wrappers first so timestamp parsing and
+        // sheet prefill below see the real link, not the wrapper.
+        let url = router.unwrapped(url)
         guard let destination = router.route(url) else { return }
 
         let action = appEnvironment.settingsManager.defaultLinkAction
@@ -671,7 +674,7 @@ struct YatteeApp: App {
             )
             LoggingService.shared.info("Deep link play: fetched video, opening player", category: .general)
             appEnvironment.toastManager.dismiss(id: toastID)
-            appEnvironment.playerService.openVideo(video, startTime: startTime)
+            appEnvironment.playerService.openVideo(video, startTime: startTime, forceStartTime: startTime != nil)
         } catch {
             LoggingService.shared.error(
                 "Deep link play: video fetch failed (\(error.localizedDescription)), falling back to info view",