chore: 简化AI模型提供商标识

- 将AI模型提供商标识从"ai-gateway"简化为"gateway"，并更新对应的Claude模型名称。

opencode.json

@@ -2,8 +2,8 @@
   "$schema": "https://opencode.ai/config.json",
   "autoupdate": "notify",
   "theme": "tokyonight",
-  "model": "ai-gateway/claude-opus-4-5-thinking",
+  "model": "gateway/claude-claude-4-5",
-  "small_model": "ai-gateway/gemini-3-flash-preview",
+  "small_model": "gateway/gemini-3-flash-preview",
   "plugin": [
     "@tarquinen/opencode-dcp@latest",
     "@franlol/opencode-md-table-formatter@latest"
@@ -26,8 +26,8 @@
     "websearch": "deny"
   },
   "provider": {
-    "ai-gateway": {
+    "gateway": {
-      "name": "AI Gateway",
+      "name": "Gateway",
       "npm": "@ai-sdk/anthropic",
       "options": {
         "baseURL": "http://10.0.1.1:8317/v1",