feat: 添加 OpenAI 兼容 API 支持和独立 Vision 服务

- 添加 OpenAI AI SDK provider 支持 (@ai-sdk/openai)
- 支持 OpenAI 兼容服务的 baseUrl 配置（如阿里云百炼）
- 添加独立的 Vision 配置（visionProvider/visionApiKey/visionBaseUrl/visionModel）
- 实现图片引用语法 @path/to/image.png，支持带空格的路径
- 当主模型不支持 vision 时，自动调用配置的 Vision 服务分析图片
- 添加图片处理工具函数和单元测试

package-lock.json

@@ -11,6 +11,7 @@
       "dependencies": {
         "@ai-sdk/anthropic": "^2.0.54",
         "@ai-sdk/deepseek": "^1.0.31",
+        "@ai-sdk/openai": "^2.0.80",
         "@tavily/core": "^0.6.0",
         "ai": "^5.0.108",
         "chalk": "^5.3.0",
@@ -88,6 +89,22 @@
         "zod": "^3.25.76 || ^4.1.8"
       }
     },
+    "node_modules/@ai-sdk/openai": {
+      "version": "2.0.80",
+      "resolved": "https://registry.npmjs.org/@ai-sdk/openai/-/openai-2.0.80.tgz",
+      "integrity": "sha512-tNHuraF11db+8xJEDBoU9E3vMcpnHFKRhnLQ3DQX2LnEzfPB9DksZ8rE+yVuDN1WRW9cm2OWAhgHFgVKs7ICuw==",
+      "license": "Apache-2.0",
+      "dependencies": {
+        "@ai-sdk/provider": "2.0.0",
+        "@ai-sdk/provider-utils": "3.0.18"
+      },
+      "engines": {
+        "node": ">=18"
+      },
+      "peerDependencies": {
+        "zod": "^3.25.76 || ^4.1.8"
+      }
+    },
     "node_modules/@ai-sdk/provider": {
       "version": "2.0.0",
       "resolved": "https://registry.npmjs.org/@ai-sdk/provider/-/provider-2.0.0.tgz",