Support non-streaming zipformer CTC ASR models (#2340)

This PR adds support for non-streaming Zipformer CTC ASR models across 
multiple language bindings, WebAssembly, examples, and CI workflows.

- Introduces a new OfflineZipformerCtcModelConfig in C/C++, Python, Swift, Java, Kotlin, Go, Dart, Pascal, and C# APIs
- Updates initialization, freeing, and recognition logic to include Zipformer CTC in WASM and Node.js
- Adds example scripts and CI steps for downloading, building, and running Zipformer CTC models

Model doc is available at
https://k2-fsa.github.io/sherpa/onnx/pretrained_models/offline-ctc/icefall/zipformer.html

flutter/sherpa_onnx/lib/src/offline_recognizer.dart

@@ -104,6 +104,27 @@ class OfflineDolphinModelConfig {
   final String model;
 }
 
+class OfflineZipformerCtcModelConfig {
+  const OfflineZipformerCtcModelConfig({this.model = ''});
+
+  factory OfflineZipformerCtcModelConfig.fromJson(Map<String, dynamic> json) {
+    return OfflineZipformerCtcModelConfig(
+      model: json['model'] as String? ?? '',
+    );
+  }
+
+  @override
+  String toString() {
+    return 'OfflineZipformerCtcModelConfig(model: $model)';
+  }
+
+  Map<String, dynamic> toJson() => {
+        'model': model,
+      };
+
+  final String model;
+}
+
 class OfflineWhisperModelConfig {
   const OfflineWhisperModelConfig(
       {this.encoder = '',
@@ -288,6 +309,7 @@ class OfflineModelConfig {
     this.moonshine = const OfflineMoonshineModelConfig(),
     this.fireRedAsr = const OfflineFireRedAsrModelConfig(),
     this.dolphin = const OfflineDolphinModelConfig(),
+    this.zipformerCtc = const OfflineZipformerCtcModelConfig(),
     required this.tokens,
     this.numThreads = 1,
     this.debug = true,
@@ -336,6 +358,10 @@ class OfflineModelConfig {
           ? OfflineDolphinModelConfig.fromJson(
               json['dolphin'] as Map<String, dynamic>)
           : const OfflineDolphinModelConfig(),
+      zipformerCtc: json['zipformerCtc'] != null
+          ? OfflineZipformerCtcModelConfig.fromJson(
+              json['zipformerCtc'] as Map<String, dynamic>)
+          : const OfflineZipformerCtcModelConfig(),
       tokens: json['tokens'] as String,
       numThreads: json['numThreads'] as int? ?? 1,
       debug: json['debug'] as bool? ?? true,
@@ -349,7 +375,7 @@ class OfflineModelConfig {
 
   @override
   String toString() {
-    return 'OfflineModelConfig(transducer: $transducer, paraformer: $paraformer, nemoCtc: $nemoCtc, whisper: $whisper, tdnn: $tdnn, senseVoice: $senseVoice, moonshine: $moonshine, fireRedAsr: $fireRedAsr, dolphin: $dolphin, tokens: $tokens, numThreads: $numThreads, debug: $debug, provider: $provider, modelType: $modelType, modelingUnit: $modelingUnit, bpeVocab: $bpeVocab, telespeechCtc: $telespeechCtc)';
+    return 'OfflineModelConfig(transducer: $transducer, paraformer: $paraformer, nemoCtc: $nemoCtc, whisper: $whisper, tdnn: $tdnn, senseVoice: $senseVoice, moonshine: $moonshine, fireRedAsr: $fireRedAsr, dolphin: $dolphin, zipformerCtc: $zipformerCtc, tokens: $tokens, numThreads: $numThreads, debug: $debug, provider: $provider, modelType: $modelType, modelingUnit: $modelingUnit, bpeVocab: $bpeVocab, telespeechCtc: $telespeechCtc)';
   }
 
   Map<String, dynamic> toJson() => {
@@ -362,6 +388,7 @@ class OfflineModelConfig {
         'moonshine': moonshine.toJson(),
         'fireRedAsr': fireRedAsr.toJson(),
         'dolphin': dolphin.toJson(),
+        'zipformerCtc': zipformerCtc.toJson(),
         'tokens': tokens,
         'numThreads': numThreads,
         'debug': debug,
@@ -381,6 +408,7 @@ class OfflineModelConfig {
   final OfflineMoonshineModelConfig moonshine;
   final OfflineFireRedAsrModelConfig fireRedAsr;
   final OfflineDolphinModelConfig dolphin;
+  final OfflineZipformerCtcModelConfig zipformerCtc;
 
   final String tokens;
   final int numThreads;
@@ -578,6 +606,8 @@ class OfflineRecognizer {
         config.model.fireRedAsr.decoder.toNativeUtf8();
 
     c.ref.model.dolphin.model = config.model.dolphin.model.toNativeUtf8();
+    c.ref.model.zipformerCtc.model =
+        config.model.zipformerCtc.model.toNativeUtf8();
 
     c.ref.model.tokens = config.model.tokens.toNativeUtf8();
 
@@ -623,6 +653,7 @@ class OfflineRecognizer {
     calloc.free(c.ref.model.modelType);
     calloc.free(c.ref.model.provider);
     calloc.free(c.ref.model.tokens);
+    calloc.free(c.ref.model.zipformerCtc.model);
     calloc.free(c.ref.model.dolphin.model);
     calloc.free(c.ref.model.fireRedAsr.decoder);
     calloc.free(c.ref.model.fireRedAsr.encoder);

flutter/sherpa_onnx/lib/src/sherpa_onnx_bindings.dart

@@ -266,6 +266,10 @@ final class SherpaOnnxOfflineDolphinModelConfig extends Struct {
   external Pointer<Utf8> model;
 }
 
+final class SherpaOnnxOfflineZipformerCtcModelConfig extends Struct {
+  external Pointer<Utf8> model;
+}
+
 final class SherpaOnnxOfflineWhisperModelConfig extends Struct {
   external Pointer<Utf8> encoder;
   external Pointer<Utf8> decoder;
@@ -333,6 +337,7 @@ final class SherpaOnnxOfflineModelConfig extends Struct {
   external SherpaOnnxOfflineMoonshineModelConfig moonshine;
   external SherpaOnnxOfflineFireRedAsrModelConfig fireRedAsr;
   external SherpaOnnxOfflineDolphinModelConfig dolphin;
+  external SherpaOnnxOfflineZipformerCtcModelConfig zipformerCtc;
 }
 
 final class SherpaOnnxOfflineRecognizerConfig extends Struct {