fix: address review issues in Expo managed workflow support

- Fix stale comment referencing RCTJavaScriptDidLoadNotification (the
  implementation uses KVO, not the notification)
- Forward unhandled KVO observations to super in
  observeValueForKeyPath:ofObject:change:context:
- Remove duplicate #import <objc/runtime.h> in SandboxReactNativeDelegate.mm
- Use a typed static context pointer (kExpoSourceUrlKVOContext) for KVO
  registration/removal instead of nil, preventing accidental dispatch of
  superclass observations into our handler
- Correct infiniteLoop comment: hangs sandbox JS thread only, host app
  stays responsive (each sandbox runs in its own Hermes instance)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: CAMOBAP

apps/expo-demo/CrashIfYouCanDemo.tsx

@@ -31,6 +31,8 @@ export default function CrashIfYouCanDemo() {
       .catch((err: any) => console.log(err.message))
   }
 
+  // Hangs the sandbox JS thread only — the host app stays responsive because
+  // each sandbox runs in its own Hermes instance and JS thread.
   const infiniteLoop = () => {
     while (true) {}
   }

packages/react-native-sandbox/ios/SandboxReactNativeDelegate.mm

@@ -17,12 +17,10 @@
 #import <React/RCTBridge+Private.h>
 #import <React/RCTBridge.h>
 #import <React/RCTBundleURLProvider.h>
-#import <objc/runtime.h>
 #import <React/RCTFollyConvert.h>
 #import <ReactAppDependencyProvider/RCTAppDependencyProvider.h>
 #import <ReactCommon/RCTInteropTurboModule.h>
 #import <ReactCommon/RCTTurboModule.h>
-
 #import <objc/runtime.h>
 
 #include <fmt/format.h>

packages/react-native-sandbox/ios/SandboxReactNativeViewComponentView.mm

@@ -39,6 +39,8 @@ static void ensureSharedFactories()
   });
 }
 
+static void *kExpoSourceUrlKVOContext = &kExpoSourceUrlKVOContext;
+
 #pragma mark - SandboxReactNativeViewComponentView
 
 @interface SandboxReactNativeViewComponentView () <RCTSandboxReactNativeViewViewProtocol>
@@ -183,11 +185,13 @@ - (void)observeValueForKeyPath:(NSString *)keyPath
                         change:(NSDictionary *)change
                        context:(void *)context
 {
-  if ([keyPath isEqualToString:@"sourceUrl"] && change[NSKeyValueChangeNewKey] != [NSNull null]) {
-    [object removeObserver:self forKeyPath:@"sourceUrl"];
+  if (context == kExpoSourceUrlKVOContext && change[NSKeyValueChangeNewKey] != [NSNull null]) {
+    [object removeObserver:self forKeyPath:@"sourceUrl" context:kExpoSourceUrlKVOContext];
     self.isObservingExpoSourceUrl = NO;
     self.didScheduleLoad = NO;
     [self scheduleReactViewLoad];
+  } else {
+    [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
   }
 }
 
@@ -227,9 +231,9 @@ - (void)loadReactNativeView
   if (!self.reactNativeFactory) {
     // Guard: verify the bundle URL is resolvable before creating the factory.
     // In Expo dev-client builds EXDevLauncherController.sourceUrl is nil until the
-    // host app JS bundle finishes loading (set in _initAppWithUrl:bundleUrl: on main thread).
-    // Rather than polling, subscribe once to RCTJavaScriptDidLoadNotification which fires
-    // after the host bundle loads — at that point sourceUrl is guaranteed to be set.
+    // host app JS bundle finishes loading (~1-2s after deep-link, set asynchronously on
+    // main thread after the network check in EXDevLauncherController completes).
+    // If it's nil we register a one-shot KVO observer and retry when it becomes non-nil.
     NSURL *resolvedURL = [self.reactNativeDelegate bundleURL];
     if (!resolvedURL) {
 #if DEBUG
@@ -246,7 +250,7 @@ - (void)loadReactNativeView
             [controller addObserver:self
                          forKeyPath:@"sourceUrl"
                             options:NSKeyValueObservingOptionNew
-                            context:nil];
+                            context:kExpoSourceUrlKVOContext];
           }
         }
       }
@@ -363,7 +367,7 @@ - (void)prepareForRecycle
     if (devLauncherClass) {
       id controller = [devLauncherClass performSelector:@selector(sharedInstance)];
       if (controller) {
-        [controller removeObserver:self forKeyPath:@"sourceUrl"];
+        [controller removeObserver:self forKeyPath:@"sourceUrl" context:kExpoSourceUrlKVOContext];
       }
     }
     self.isObservingExpoSourceUrl = NO;
@@ -380,7 +384,7 @@ - (void)dealloc
     if (devLauncherClass) {
       id controller = [devLauncherClass performSelector:@selector(sharedInstance)];
       if (controller) {
-        [controller removeObserver:self forKeyPath:@"sourceUrl"];
+        [controller removeObserver:self forKeyPath:@"sourceUrl" context:kExpoSourceUrlKVOContext];
       }
     }
     self.isObservingExpoSourceUrl = NO;