Nomad changes

docs/snippets/dart/plugins/stateful_plugin.md

@@ -0,0 +1,16 @@
+<!-- snippet:skip reason="Dart cannot construct the opaque BoxFn closure types required by createPostProcessorDartImpl — flutter_rust_bridge generates them as RustOpaqueInterface with no Dart-side wrapper. The closure-captured state pattern is therefore unreachable. Custom plugins must be written in Rust." -->
+```dart title="Dart"
+import 'package:kreuzberg/kreuzberg.dart';
+
+Future<void> main() async {
+  // A stateful Dart `PostProcessor` that captures mutable counters in its
+  // closure cannot be plugged into the global registry.
+  // `Kreuzberg.registerPostProcessor(impl)` exists, but the
+  // `createPostProcessorDartImpl` factory takes opaque `BoxFn*` closure
+  // values whose constructors are not surfaced through flutter_rust_bridge,
+  // so the closure-capture pattern is unreachable from Dart.
+  //
+  // Implement stateful plugins in Rust using `Mutex`/`AtomicU64` for
+  // interior mutability, then register them in a Rust shim crate.
+}
+```