remove scaffold getPlatformVersion across all platform plugins

`getPlatformVersion` was the example method from
`flutter create --template=plugin` — a sanity-check that returns a
string like "macOS 14.5.0". Nothing in this workspace nor flet itself
ever called `SeriousPython.getPlatformVersion()`; the only consumers
were the scaffold-generated plugin tests for Linux and Windows. Drop
it everywhere before the dart-bridge release.

Touches all six packages:
- Top-level facade + platform-interface + method-channel impl: drop
  the declaration / forwarding wrapper.
- Linux & Windows Dart impls: drop the override and the now-unused
  `methodChannel` field; trim the corresponding flutter/services and
  flutter/foundation imports.
- Linux native plugin (C): drop the `get_platform_version()` function,
  collapse the method-call handler to a `NotImplemented` stub, and
  remove the now-orphan `<sys/utsname.h>`, `<cstring>`, and
  `_plugin_private.h` includes. Delete `_plugin_private.h` (only ever
  declared this function) and `linux/test/` (only tested this function;
  not referenced by CMakeLists).
- Windows native plugin (C++): same shape — drop the case, the
  `<VersionHelpers.h>` + `<sstream>` includes, and the entire
  `windows/test/` scaffold.
- Darwin Swift: drop the `getPlatformVersion` case; the `getResourcePath`
  case stays. Tighten the file docstring accordingly.
- Android Java: drop the `getPlatformVersion` if-arm;
  `getAppVersion` / `getNativeLibraryDir` stay.

flutter analyze: clean across all six packages (the 6 remaining
warnings are pre-existing path-dep / missing-asset notes from local
dev setup, unrelated to this change).

Technically a public API break — `SeriousPython.getPlatformVersion()`
is part of the published Dart API — but folded in here with the
dart-bridge wire-format break already in flight.

Author: FeodorFitsner

src/serious_python/lib/serious_python.dart

@@ -9,11 +9,6 @@ export 'package:serious_python_platform_interface/src/utils.dart';
 class SeriousPython {
   SeriousPython._();
 
-  /// Returns the current name and version of the operating system.
-  static Future<String?> getPlatformVersion() {
-    return SeriousPythonPlatform.instance.getPlatformVersion();
-  }
-
   /// Runs Python program from an asset.
   ///
   /// [assetPath] is the path to an asset which is a zip archive

src/serious_python_android/android/src/main/java/com/flet/serious_python_android/AndroidPlugin.java

@@ -58,9 +58,7 @@ public void onAttachedToActivity(@NonNull ActivityPluginBinding activityPluginBi
 
   @Override
   public void onMethodCall(@NonNull MethodCall call, @NonNull Result result) {
-    if (call.method.equals("getPlatformVersion")) {
-      result.success("Android " + android.os.Build.VERSION.RELEASE);
-    } else if (call.method.equals("getAppVersion")) {
+    if (call.method.equals("getAppVersion")) {
       try {
         String packageName = context.getPackageName();
         android.content.pm.PackageManager pm = context.getPackageManager();

src/serious_python_android/lib/serious_python_android.dart

@@ -26,10 +26,6 @@ class SeriousPythonAndroid extends SeriousPythonPlatform {
     SeriousPythonPlatform.instance = SeriousPythonAndroid();
   }
 
-  @override
-  Future<String?> getPlatformVersion() =>
-      methodChannel.invokeMethod<String>('getPlatformVersion');
-
   @override
   Future<String?> run(String appPath,
       {String? script,

src/serious_python_darwin/darwin/Classes/SeriousPythonPlugin.swift

@@ -16,9 +16,9 @@ private func _sp_init_keepalive(_ data: UnsafeMutableRawPointer?) -> Int
 @_silgen_name("DartBridge_EnqueueMessage")
 private func _sp_enqueue_keepalive(_ data: UnsafePointer<CChar>?, _ len: Int)
 
-/// Thin Flutter plugin: surfaces the python.bundle resource path to Dart and
-/// exposes the standard `getPlatformVersion`. All Python lifecycle now lives
-/// in `serious_python_run` (dart_bridge.xcframework), invoked from Dart.
+/// Thin Flutter plugin: surfaces the python.bundle resource path to Dart.
+/// All Python lifecycle now lives in `serious_python_run`
+/// (dart_bridge.xcframework), invoked from Dart.
 public class SeriousPythonPlugin: NSObject, FlutterPlugin {
 
     public static func register(with registrar: FlutterPluginRegistrar) {
@@ -44,13 +44,6 @@ public class SeriousPythonPlugin: NSObject, FlutterPlugin {
 
     public func handle(_ call: FlutterMethodCall, result: @escaping FlutterResult) {
         switch call.method {
-        case "getPlatformVersion":
-            #if os(iOS)
-                result("iOS " + UIDevice.current.systemVersion)
-            #else
-                result("macOS " + ProcessInfo.processInfo.operatingSystemVersionString)
-            #endif
-
         case "getResourcePath":
             // The python.bundle that prepare_{ios,macos}.sh assembles ends up
             // inside this plugin's framework bundle as a Resources subbundle.

src/serious_python_darwin/lib/serious_python_darwin.dart

@@ -17,10 +17,6 @@ class SeriousPythonDarwin extends SeriousPythonPlatform {
     SeriousPythonPlatform.instance = SeriousPythonDarwin();
   }
 
-  @override
-  Future<String?> getPlatformVersion() =>
-      methodChannel.invokeMethod<String>('getPlatformVersion');
-
   @override
   Future<String?> run(String appPath,
       {String? script,

src/serious_python_linux/lib/serious_python_linux.dart

@@ -1,7 +1,5 @@
 import 'dart:io';
 
-import 'package:flutter/foundation.dart';
-import 'package:flutter/services.dart';
 import 'package:path/path.dart' as p;
 import 'package:serious_python_platform_interface/serious_python_platform_interface.dart';
 
@@ -20,20 +18,10 @@ import 'package:serious_python_platform_interface/serious_python_platform_interf
 ///    doesn't have a compile-time constant for it).
 /// 3. Hands env + sys.path to `serious_python_run` in a single FFI call.
 class SeriousPythonLinux extends SeriousPythonPlatform {
-  @visibleForTesting
-  final methodChannel = const MethodChannel('serious_python_linux');
-
   static void registerWith() {
     SeriousPythonPlatform.instance = SeriousPythonLinux();
   }
 
-  @override
-  Future<String?> getPlatformVersion() async {
-    final version =
-        await methodChannel.invokeMethod<String>('getPlatformVersion');
-    return '$version ${Platform.resolvedExecutable}';
-  }
-
   @override
   Future<String?> run(String appPath,
       {String? script,

src/serious_python_linux/linux/serious_python_linux_plugin.cc

@@ -2,14 +2,9 @@
 
 #include <flutter_linux/flutter_linux.h>
 #include <gtk/gtk.h>
-#include <sys/utsname.h>
 
-#include <cstring>
-
-#include "serious_python_linux_plugin_private.h"
-
-// Thin Flutter plugin: only surfaces the OS version. Python lifecycle now
-// lives in libdart_bridge.so, invoked from Dart via FFI.
+// Plugin-registration shell only — all method calls return NotImplemented.
+// Python lifecycle lives in libdart_bridge.so, invoked from Dart via FFI.
 
 #define SERIOUS_PYTHON_LINUX_PLUGIN(obj)                                     \
   (G_TYPE_CHECK_INSTANCE_CAST((obj), serious_python_linux_plugin_get_type(), \
@@ -26,30 +21,11 @@ static void serious_python_linux_plugin_handle_method_call(
     SeriousPythonLinuxPlugin *self,
     FlMethodCall *method_call)
 {
-  g_autoptr(FlMethodResponse) response = nullptr;
-  const gchar *method = fl_method_call_get_name(method_call);
-
-  if (strcmp(method, "getPlatformVersion") == 0)
-  {
-    response = get_platform_version();
-  }
-  else
-  {
-    response = FL_METHOD_RESPONSE(fl_method_not_implemented_response_new());
-  }
-
+  g_autoptr(FlMethodResponse) response =
+      FL_METHOD_RESPONSE(fl_method_not_implemented_response_new());
   fl_method_call_respond(method_call, response, nullptr);
 }
 
-FlMethodResponse *get_platform_version()
-{
-  struct utsname uname_data = {};
-  uname(&uname_data);
-  g_autofree gchar *version = g_strdup_printf("Linux %s", uname_data.version);
-  g_autoptr(FlValue) result = fl_value_new_string(version);
-  return FL_METHOD_RESPONSE(fl_method_success_response_new(result));
-}
-
 static void serious_python_linux_plugin_dispose(GObject *object)
 {
   G_OBJECT_CLASS(serious_python_linux_plugin_parent_class)->dispose(object);

src/serious_python_linux/linux/serious_python_linux_plugin_private.h

@@ -26,10 +26,6 @@ abstract class SeriousPythonPlatform extends PlatformInterface {
     _instance = instance;
   }
 
-  Future<String?> getPlatformVersion() {
-    throw UnimplementedError('platformVersion() has not been implemented.');
-  }
-
   Future<String?> run(String appPath,
       {String? script,
       List<String>? modulePaths,