fix(mobile): open the OTA workspace page on iOS 18 (#29197)

WebKit reports no source frame for an app-initiated load() before iOS 18.5 (WebKit c28b242), so the iOS shell read its own document load as subframe-initiated and cancelled it, leaving the phone on "Opening workspace" forever. The navigation policy no longer takes the initiating frame as an input: the shell's own document loads when its one-shot load flag is up, the URL is the exact document URL, the target is the main frame, and it is not a download, matching the Android copy.

Verified on an iOS 18.1 simulator (hang before, workspace opens after) and iOS 26.5 (unchanged).

Refs #28626, STA-10545

mobile/modules/orca-mobile-web-shell/ios/MobileWebShellNavigationPolicy.swift

@@ -41,9 +41,9 @@ enum MobileWebShellNavigationPolicy {
   /// WKWebView, off-device: a sandboxed subframe navigating the top frame to the document URL
   /// arrives as `.other` with no gesture at all, and under a gesture-shaped rule that is an allow
   /// and a shell reload -- the bridge target cleared, the load state restarted, the page's state
-  /// gone. `isFromSubframe` is the second discriminator for the same reason: the same probe shows
-  /// the shell's own load arriving with source and target both the main frame, and a subframe's top
-  /// navigation arriving with the subframe as its source.
+  /// gone. The initiating frame is deliberately not an input: before iOS 18.5 WebKit reports no
+  /// source frame for the view's own `load` (WebKit c28b242), and reading it refused the shell's
+  /// own document. The one-shot flag already refuses a subframe's top navigation, as on Android.
   ///
   /// What is left for the gesture is the only thing an artifact may ask for: a foreign URL, which
   /// is refused and handed to the opener. A download is not a document load, so it takes that path
@@ -56,7 +56,6 @@ enum MobileWebShellNavigationPolicy {
   static func verdict(
     url: String?,
     isMainFrame: Bool,
-    isFromSubframe: Bool,
     isDocumentUrl: Bool,
     isShellLoad: Bool,
     hasGesture: Bool,
@@ -66,7 +65,7 @@ enum MobileWebShellNavigationPolicy {
       return .cancel
     }
     if isDocumentUrl {
-      return isShellLoad && !isFromSubframe && !isDownload ? .allow : .cancel
+      return isShellLoad && !isDownload ? .allow : .cancel
     }
     guard hasGesture, let offered = offerableUrl(url) else {
       return .cancel

mobile/modules/orca-mobile-web-shell/ios/MobileWebShellView.swift

@@ -479,7 +479,6 @@ final class OrcaMobileWebShellView: ExpoView, WKNavigationDelegate, WKUIDelegate
     let verdict = MobileWebShellNavigationPolicy.verdict(
       url: navigationAction.request.url?.absoluteString,
       isMainFrame: navigationAction.targetFrame?.isMainFrame == true,
-      isFromSubframe: !navigationAction.sourceFrame.isMainFrame,
       isDocumentUrl: isDocumentUrl(navigationAction.request.url),
       isShellLoad: loadState.isShellLoad,
       hasGesture: navigationAction.navigationType == .linkActivated,

mobile/modules/orca-mobile-web-shell/tests/MobileWebShellChecks.swift

@@ -545,7 +545,6 @@ import Foundation
     func verdict(
       _ url: String? = "https://example.com/artifact-link",
       isMainFrame: Bool = true,
-      isFromSubframe: Bool = false,
       isDocumentUrl: Bool = false,
       isShellLoad: Bool = false,
       hasGesture: Bool = true,
@@ -554,7 +553,6 @@ import Foundation
       MobileWebShellNavigationPolicy.verdict(
         url: url,
         isMainFrame: isMainFrame,
-        isFromSubframe: isFromSubframe,
         isDocumentUrl: isDocumentUrl,
         isShellLoad: isShellLoad,
         hasGesture: hasGesture,
@@ -571,18 +569,14 @@ import Foundation
     // navigating the top frame to the document URL arrives with no gesture at all.
     precondition(verdict(document, isDocumentUrl: true, hasGesture: false) == .cancel)
     precondition(verdict(document, isDocumentUrl: true, hasGesture: true) == .cancel)
-    precondition(
-      verdict(document, isFromSubframe: true, isDocumentUrl: true, isShellLoad: true, hasGesture: false)
-        == .cancel
-    )
-    // The second discriminator, on its own: a load the shell did not start is refused even when the
-    // initiating frame is the main one, which is the page rewriting its own document away.
+    // A load the shell did not start is refused whichever frame initiated it: the page rewriting
+    // its own document away, or the sealed preview navigating the top frame.
     precondition(verdict(document, isDocumentUrl: true, isShellLoad: false, hasGesture: false) == .cancel)
     // A top-page meta refresh or a redirect to somewhere else: refused, and never opened.
     precondition(verdict(hasGesture: false) == .cancel)
     // A tap inside the sealed preview is exactly a subframe-initiated foreign navigation, and that
     // is the one thing the artifact is allowed to ask for.
-    precondition(verdict(isFromSubframe: true) == .cancelAndOffer(foreign))
+    precondition(verdict() == .cancelAndOffer(foreign))
     // A download is not a document load, so it is refused there rather than allowed; started by a
     // tap it reaches the opener, which is what makes `<a download>` behave as it does natively.
     precondition(
@@ -591,11 +585,8 @@ import Foundation
     )
     precondition(verdict(isDownload: true) == .cancelAndOffer(foreign))
     // `<a href="/" download>`: a download that still names the shell's own document, which is the
-    // one thing never handed to the opener. Refused from either frame, gesture or not.
+    // one thing never handed to the opener. Refused, gesture or not.
     precondition(verdict(document, isDocumentUrl: true, isDownload: true) == .cancel)
-    precondition(
-      verdict(document, isFromSubframe: true, isDocumentUrl: true, isDownload: true) == .cancel
-    )
     // A subframe is the sealed preview loading itself, which is not the user leaving the app.
     precondition(verdict(isMainFrame: false) == .cancel)
     precondition(verdict(isMainFrame: false, hasGesture: false) == .cancel)
@@ -624,7 +615,6 @@ import Foundation
       MobileWebShellNavigationPolicy.verdict(
         url: document,
         isMainFrame: true,
-        isFromSubframe: false,
         isDocumentUrl: true,
         isShellLoad: machine.isShellLoad,
         hasGesture: false,