feat: Introduce a pluggable LLM provider system with token extraction, pricing, and updated setup configuration.

Providers/ProviderFactory.cs

@@ -0,0 +1,70 @@
+namespace AnchorCli.Providers;
+
+/// <summary>
+/// Factory for creating provider instances based on endpoint or provider name.
+/// </summary>
+internal static class ProviderFactory
+{
+    /// <summary>
+    /// Creates a token extractor based on the provider name.
+    /// </summary>
+    public static ITokenExtractor CreateTokenExtractor(string providerName)
+    {
+        return providerName.ToLowerInvariant() switch
+        {
+            "openrouter" => new OpenRouterTokenExtractor(),
+            "groq" => new GroqTokenExtractor(),
+            "ollama" => new OllamaTokenExtractor(),
+            _ => new GenericTokenExtractor()
+        };
+    }
+
+    /// <summary>
+    /// Creates a token extractor by auto-detecting from the endpoint URL.
+    /// </summary>
+    public static ITokenExtractor CreateTokenExtractorForEndpoint(string endpoint)
+    {
+        if (string.IsNullOrEmpty(endpoint))
+        {
+            return new GenericTokenExtractor();
+        }
+
+        var url = endpoint.ToLowerInvariant();
+
+        if (url.Contains("openrouter"))
+        {
+            return new OpenRouterTokenExtractor();
+        }
+
+        if (url.Contains("groq"))
+        {
+            return new GroqTokenExtractor();
+        }
+
+        if (url.Contains("ollama") || url.Contains("localhost") || url.Contains("127.0.0.1"))
+        {
+            return new OllamaTokenExtractor();
+        }
+
+        return new GenericTokenExtractor();
+    }
+
+    /// <summary>
+    /// Creates a pricing provider based on the provider name.
+    /// Only OpenRouter has a pricing API currently.
+    /// </summary>
+    public static IPricingProvider? CreatePricingProvider(string providerName)
+    {
+        return providerName.ToLowerInvariant() switch
+        {
+            "openrouter" => new OpenRouterProvider(),
+            _ => null  // Other providers don't have pricing APIs yet
+        };
+    }
+
+    /// <summary>
+    /// Determines if an endpoint is OpenRouter.
+    /// </summary>
+    public static bool IsOpenRouter(string endpoint) =>
+        !string.IsNullOrEmpty(endpoint) && endpoint.Contains("openrouter", StringComparison.OrdinalIgnoreCase);
+}