feat(providers): add Minimax Coding (China) provider

- Add minimax-cn provider with China endpoint (api.minimaxi.com)
- Add provider icon and configuration
- Add validation and test support
- Add API configuration in open-sse

Co-authored-by: Blade096 <46746496+Blade096@users.noreply.github.com>
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
Co-authored-by: Cursor <cursoragent@cursor.com>

open-sse/executors/default.js

@@ -23,6 +23,7 @@ export class DefaultExecutor extends BaseExecutor {
       case "glm":
       case "kimi":
       case "minimax":
+      case "minimax-cn":
         return `${this.config.baseUrl}?beta=true`;
       case "gemini":
         return `${this.config.baseUrl}/${model}:${stream ? "streamGenerateContent?alt=sse" : "generateContent"}`;
@@ -44,6 +45,7 @@ export class DefaultExecutor extends BaseExecutor {
       case "glm":
       case "kimi":
       case "minimax":
+      case "minimax-cn":
         headers["x-api-key"] = credentials.apiKey;
         break;
       default: