Initial commit: Text encoding component with UTF-8 polyfills

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

TextEncodingService.ts

@@ -0,0 +1,89 @@
+/**
+ * Text Encoding Service Implementation
+ *
+ * Provides shared encoder/decoder instances with automatic polyfill fallback
+ *
+ * @module text-encoding@1.0.0
+ */
+
+import type { ITextDecoder, ITextEncoder, ITextEncodingService } from './interfaces';
+import { TextDecoderPolyfill } from './TextDecoderPolyfill';
+import { TextEncoderPolyfill } from './TextEncoderPolyfill';
+
+export class TextEncodingService implements ITextEncodingService {
+  readonly encoder: ITextEncoder;
+  readonly decoder: ITextDecoder;
+
+  constructor() {
+    // Check for native support and use it if available
+    if (this.hasNativeSupport()) {
+      // Use native implementations if available
+      // @ts-expect-error - TextEncoder might exist globally
+      this.encoder =
+        typeof TextEncoder !== 'undefined' ? new TextEncoder() : new TextEncoderPolyfill();
+
+      // @ts-expect-error - TextDecoder might exist globally
+      this.decoder =
+        typeof TextDecoder !== 'undefined' ? new TextDecoder() : new TextDecoderPolyfill();
+    } else {
+      // Use polyfills
+      this.encoder = new TextEncoderPolyfill();
+      this.decoder = new TextDecoderPolyfill();
+    }
+  }
+
+  /**
+   * Check if native TextEncoder/TextDecoder are available
+   */
+  private hasNativeSupport(): boolean {
+    // @ts-expect-error - Check global scope
+    return typeof TextEncoder !== 'undefined' && typeof TextDecoder !== 'undefined';
+  }
+
+  /**
+   * Encode string to UTF-8 bytes
+   */
+  encode(text: string): Uint8Array {
+    return this.encoder.encode(text);
+  }
+
+  /**
+   * Decode bytes to string
+   */
+  decode(bytes: Uint8Array | ArrayBuffer | number[]): string {
+    if (Array.isArray(bytes)) {
+      // Convert number array to Uint8Array
+      return this.decoder.decode(new Uint8Array(bytes));
+    }
+    return this.decoder.decode(bytes as Uint8Array | ArrayBuffer);
+  }
+
+  /**
+   * Convenience method: string to UTF-8
+   */
+  stringToUtf8(text: string): Uint8Array {
+    return this.encode(text);
+  }
+
+  /**
+   * Convenience method: UTF-8 to string
+   */
+  utf8ToString(bytes: Uint8Array | number[]): string {
+    return this.decode(bytes);
+  }
+}
+
+/**
+ * Singleton instance for shared use
+ */
+let serviceInstance: TextEncodingService | null = null;
+
+/**
+ * Get or create the singleton service instance
+ */
+export function getTextEncodingService(): ITextEncodingService {
+  if (!serviceInstance) {
+    serviceInstance = new TextEncodingService();
+  }
+  return serviceInstance;
+}