Add Minimax CustomProvider

Adds CustomProviders.Minimax() factory method with base URL https://api.minimax.io/v1
for the MiniMax AI platform (MiniMax-M2.7, M2.5) which uses OpenAI-compatible endpoints.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: HavenDV

src/libs/tryAGI.OpenAI/CustomProviders.cs

@@ -106,6 +106,11 @@ public static class CustomProviders
     /// </summary>
     public const string OllamaCloudBaseUrl = "https://ollama.com/api/v1";
 
+    /// <summary>
+    /// https://platform.minimax.io/docs/api-reference
+    /// </summary>
+    public const string MinimaxBaseUrl = "https://api.minimax.io/v1";
+
     /// <summary>
     /// Creates an API to use for GitHub Models: https://github.com/marketplace/models
     /// </summary>
@@ -294,4 +299,13 @@ public static OpenAiClient OllamaCloud(string apiKey)
     {
         return new OpenAiClient(apiKey, baseUri: new Uri(OllamaCloudBaseUrl));
     }
+
+    /// <summary>
+    /// Create an API to use for MiniMax.
+    /// </summary>
+    /// <returns></returns>
+    public static OpenAiClient Minimax(string apiKey)
+    {
+        return new OpenAiClient(apiKey, baseUri: new Uri(MinimaxBaseUrl));
+    }
 }