Remove prefersFuseboxFrontend capability flag (#55550)

Summary:
Pull Request resolved: #55550

**Context**

Clean up the legacy `rn_inspector.html` entry point. React Native DevTools has been the default since 0.76, and we have now removed all internal dependencies at Meta.

We've verified that Reanimated (`react-native-worklets`) also do not depend on this workflow, and documents `chrome://inspect` instead.

**This diff**

- Remove the `prefersFuseboxFrontend` capability flag from device pages.

Changelog:
[General][Changed] - **React Native DevTools**: Page targets returned from `/json/list` will no longer set `prefersFuseboxFrontend`

Reviewed By: vzaidman

Differential Revision: D93247603

fbshipit-source-id: 4a4cb06476d3e44c3124d0b5a5d942b6880a561a

Author: huntie

packages/react-native/React/Base/RCTBridge.mm

@@ -583,7 +583,7 @@ - (void)setUp
           }
           return strongSelf->_inspectorTarget->connect(std::move(remote));
         },
-        {.nativePageReloads = true, .prefersFuseboxFrontend = true});
+        {.nativePageReloads = true});
   }
 
   Class bridgeClass = self.bridgeClass;

packages/react-native/ReactAndroid/src/main/jni/react/runtime/jni/JReactHostInspectorTarget.cpp

@@ -48,7 +48,7 @@ JReactHostInspectorTarget::JReactHostInspectorTarget(
           // Reject the connection.
           return nullptr;
         },
-        {.nativePageReloads = true, .prefersFuseboxFrontend = true});
+        {.nativePageReloads = true});
   }
 }
 

packages/react-native/ReactCommon/jsinspector-modern/InspectorInterfaces.cpp

@@ -29,8 +29,7 @@ folly::dynamic targetCapabilitiesToDynamic(
     const InspectorTargetCapabilities& capabilities) {
   return folly::dynamic::object(
       "nativePageReloads", capabilities.nativePageReloads)(
-      "nativeSourceCodeFetching", capabilities.nativeSourceCodeFetching)(
-      "prefersFuseboxFrontend", capabilities.prefersFuseboxFrontend);
+      "nativeSourceCodeFetching", capabilities.nativeSourceCodeFetching);
 }
 
 namespace {
@@ -143,16 +142,6 @@ int InspectorImpl::addPage(
       pageId,
       Page{pageId, description, vm, std::move(connectFunc), capabilities});
 
-  // Strong assumption: If prefersFuseboxFrontend is set, the page added is a
-  // HostTarget and not a legacy Hermes runtime target.
-  if (capabilities.prefersFuseboxFrontend) {
-    for (const auto& listenerWeak : listeners_) {
-      if (auto listener = listenerWeak.lock()) {
-        listener->unstable_onHostTargetAdded();
-      }
-    }
-  }
-
   return pageId;
 }
 

packages/react-native/ReactCommon/jsinspector-modern/InspectorInterfaces.h

@@ -36,7 +36,6 @@ class IDestructible {
 struct InspectorTargetCapabilities {
   bool nativePageReloads = false;
   bool nativeSourceCodeFetching = false;
-  bool prefersFuseboxFrontend = false;
 };
 
 folly::dynamic targetCapabilitiesToDynamic(const InspectorTargetCapabilities &capabilities);

packages/react-native/ReactCommon/react/runtime/platform/ios/ReactCommon/RCTHost.mm

@@ -255,7 +255,7 @@ - (void)start
           }
           return strongSelf->_inspectorTarget->connect(std::move(remote));
         },
-        {.nativePageReloads = true, .prefersFuseboxFrontend = true});
+        {.nativePageReloads = true});
   }
   if (_instance) {
     RCTLogWarn(

packages/react-native/ReactCxxPlatform/react/devsupport/inspector/Inspector.cpp

@@ -180,7 +180,7 @@ void Inspector::ensureHostTarget(
       });
   static_cast<InspectorHostTargetDelegate&>(*hostDelegate_).setTarget(target_);
   jsinspector_modern::InspectorTargetCapabilities capabilities{
-      .nativePageReloads = true, .prefersFuseboxFrontend = true};
+      .nativePageReloads = true};
   pageId_ = jsinspector_modern::getInspectorInstance().addPage(
       std::string(INTEGRATION_NAME),
       "", /*vm*/