Address review feedback from original PR #457

- Break circular import between native_functions.dart and dart_bridge_vad.dart
  by moving RacVadResultStruct into ffi_types.dart (where every other FFI
  struct lives). native_functions.dart no longer needs to import the VAD
  bridge.
- Remove dead NativeFunctions.sttResultFree entry. The STT transcription
  path runs inside Isolate.run(...) and resolves rac_stt_result_free with
  its own inline lookup (isolates can't see main-isolate statics), so the
  cached main-isolate entry was never reachable. Left a short comment in
  its place explaining why.

Author: sanchitmonga22

sdk/runanywhere-flutter/packages/runanywhere/lib/native/dart_bridge_vad.dart

@@ -329,15 +329,3 @@ class VADSpeechEndedEvent extends VADActivityEvent {
 
   const VADSpeechEndedEvent({required this.energy});
 }
-
-/// FFI struct for VAD result (matches rac_vad_result_t)
-final class RacVadResultStruct extends Struct {
-  @Int32()
-  external int isSpeech;
-
-  @Float()
-  external double energy;
-
-  @Float()
-  external double speechProbability;
-}

sdk/runanywhere-flutter/packages/runanywhere/lib/native/ffi_types.dart

@@ -1039,6 +1039,18 @@ base class RacVadOnnxResultStruct extends Struct {
   external double probability;
 }
 
+/// VAD result struct matching rac_vad_result_t
+base class RacVadResultStruct extends Struct {
+  @Int32()
+  external int isSpeech;
+
+  @Float()
+  external double energy;
+
+  @Float()
+  external double speechProbability;
+}
+
 // =============================================================================
 // VLM API Types (from rac_vlm_types.h)
 // =============================================================================

sdk/runanywhere-flutter/packages/runanywhere/lib/native/native_functions.dart

@@ -12,7 +12,6 @@ import 'dart:ffi';
 import 'package:ffi/ffi.dart';
 import 'package:runanywhere/native/ffi_types.dart';
 import 'package:runanywhere/native/platform_loader.dart';
-import 'package:runanywhere/native/dart_bridge_vad.dart' as vad;
 
 /// Cached native function pointers for the RACommons library.
 ///
@@ -87,9 +86,11 @@ abstract class NativeFunctions {
       _lib.lookupFunction<Int32 Function(RacHandle), int Function(RacHandle)>(
           'rac_stt_component_cleanup');
 
-  static final void Function(Pointer<RacSttResultStruct>) sttResultFree =
-      _lib.lookupFunction<Void Function(Pointer<RacSttResultStruct>),
-          void Function(Pointer<RacSttResultStruct>)>('rac_stt_result_free');
+  // Note: rac_stt_result_free is intentionally NOT cached here. The STT
+  // transcription path runs inside Isolate.run(...), which cannot access
+  // main-isolate static state — `_transcribeInIsolate` in dart_bridge_stt.dart
+  // performs its own inline lookup so each spawned isolate resolves the
+  // symbol once. A main-isolate cache entry would be dead code.
 
   static final void Function(RacHandle) sttDestroy =
       _lib.lookupFunction<Void Function(RacHandle), void Function(RacHandle)>(
@@ -177,19 +178,19 @@ abstract class NativeFunctions {
     RacHandle,
     Pointer<Float>,
     int,
-    Pointer<vad.RacVadResultStruct>,
+    Pointer<RacVadResultStruct>,
   ) vadProcess = _lib.lookupFunction<
       Int32 Function(
         RacHandle,
         Pointer<Float>,
         IntPtr,
-        Pointer<vad.RacVadResultStruct>,
+        Pointer<RacVadResultStruct>,
       ),
       int Function(
         RacHandle,
         Pointer<Float>,
         int,
-        Pointer<vad.RacVadResultStruct>,
+        Pointer<RacVadResultStruct>,
       )>('rac_vad_component_process');
 
   static final void Function(RacHandle) vadDestroy =