fix: add option for overriding API Url for Moonshot provider (#9819)

crates/goose/src/providers/declarative/moonshot.json

@@ -2,9 +2,18 @@
   "name": "moonshot",
   "engine": "openai",
   "display_name": "Moonshot",
-  "description": "Moonshot AI (Kimi) models",
+  "description": "Moonshot AI (Kimi) models. Set MOONSHOT_BASE_URL to override the default endpoint (e.g. https://api.moonshot.ai/v1 for international users).",
   "api_key_env": "MOONSHOT_API_KEY",
-  "base_url": "https://api.moonshot.cn/v1/chat/completions",
+  "base_url": "${MOONSHOT_BASE_URL}",
+  "env_vars": [
+    {
+      "name": "MOONSHOT_BASE_URL",
+      "required": false,
+      "secret": false,
+      "default": "https://api.moonshot.cn/v1/chat/completions",
+      "description": "Moonshot API base URL. Use https://api.moonshot.ai/v1 for international access outside China Mainland."
+    }
+  ],
   "models": [
     {"name": "kimi-latest", "context_limit": 131072},
     {"name": "kimi-thinking-preview", "context_limit": 131072},