Fix IntelliJ IDEA project open silent failure by removing FlutterProjectOpenProcessor

FlutterProjectOpenProcessor silently failed to open Flutter projects
without a .idea directory because getDelegateImportProvider() returned
null when no other processor could claim the project. Since this
processor was registered with order="first", no fallback occurred.

Apply the same fix pattern as PR flutter#8710 (Android Studio):
- Remove FlutterProjectOpenProcessor.kt
- Remove its <projectOpenProcessor> registration from plugin.xml
- Add module-type-fixing logic to FlutterInitializer (startup activity)
- Add changelog entry

This lets the platform's default project opener handle opening, then
FlutterInitializer configures Flutter module type and Dart SDK after
the project is loaded.

Fixes flutter#8845

Author: Georgii Kostenko

CHANGELOG.md

@@ -10,6 +10,8 @@
 
 ### Fixed
 
+- Fixed silent failure when opening Flutter projects without `.idea` directory in IntelliJ IDEA by removing `FlutterProjectOpenProcessor` and migrating configuration logic to `FlutterInitializer`. (#8845)
+
 ## 90.0.0
 
 ### Added

resources/META-INF/plugin.xml

@@ -335,8 +335,6 @@
     <!-- See https://github.com/flutter/flutter-intellij/issues/8029 -->
     <projectService serviceImplementation="io.flutter.view.InspectorView" overrides="false"/>
 
-    <projectOpenProcessor id="flutter" implementation="io.flutter.project.FlutterProjectOpenProcessor" order="first"/>
-
     <editorNotificationProvider implementation="io.flutter.editor.FlutterPubspecNotificationProvider"/>
     <editorNotificationProvider implementation="io.flutter.inspections.SdkConfigurationNotificationProvider"/>
     <editorNotificationProvider implementation="io.flutter.editor.NativeEditorNotificationProvider"/>

src/io/flutter/FlutterInitializer.java

@@ -67,8 +67,6 @@
  * Runs actions after the project has started up and the index is up to date.
  *
  * @see ProjectOpenActivity for actions that run earlier.
- * @see io.flutter.project.FlutterProjectOpenProcessor for additional actions that
- * may run when a project is being imported.
  */
 public class FlutterInitializer extends FlutterProjectActivity {
   private boolean toolWindowsInitialized = false;
@@ -97,6 +95,18 @@ public void executeProjectStartup(@NotNull Project project) {
     // Start a DevTools server
     DevToolsService.getInstance(project);
 
+    // Ensure Flutter project configuration is applied for projects that may have been
+    // opened without a .idea directory. Previously this was handled by FlutterProjectOpenProcessor,
+    // but that processor silently failed when no delegate processor could open the project.
+    // Instead, we let the platform open the project normally and apply our configuration here.
+    // See https://github.com/flutter/flutter-intellij/issues/8661 (Android Studio equivalent)
+    for (Module module : FlutterModuleUtils.getModules(project)) {
+      if (FlutterModuleUtils.declaresFlutter(module) && !FlutterModuleUtils.isFlutterModule(module)) {
+        log().info("Fixing Flutter module configuration for " + module.getName());
+        FlutterModuleUtils.setFlutterModuleAndReload(module, project);
+      }
+    }
+
     // If the project declares a Flutter dependency, do some extra initialization.
     boolean hasFlutterModule = false;