fix(gemini): 更新 Gemini 模型列表配置

- 移除已弃用的 1.5 系列模型
- 调整模型优先级顺序（2.0 Flash > 2.5 Flash > 2.5 Pro > 3.0 Preview）
- 同步前后端模型配置
- 更新相关测试用例和默认模型选择逻辑

frontend/src/components/keys/UseKeyModal.vue

@@ -443,7 +443,7 @@ $env:ANTHROPIC_AUTH_TOKEN="${apiKey}"`
 }
 
 function generateGeminiCliContent(baseUrl: string, apiKey: string): FileConfig {
-  const model = 'gemini-2.5-pro'
+  const model = 'gemini-2.0-flash'
   const modelComment = t('keys.useKeyModal.gemini.modelComment')
   let path: string
   let content: string
@@ -548,14 +548,22 @@ function generateOpenCodeConfig(platform: string, baseUrl: string, apiKey: strin
     }
   }
   const geminiModels = {
-    'gemini-3-pro-high': { name: 'Gemini 3 Pro High' },
-    'gemini-3-pro-low': { name: 'Gemini 3 Pro Low' },
-    'gemini-3-pro-preview': { name: 'Gemini 3 Pro Preview' },
-    'gemini-3-pro-image': { name: 'Gemini 3 Pro Image' },
-    'gemini-3-flash': { name: 'Gemini 3 Flash' },
-    'gemini-2.5-flash-thinking': { name: 'Gemini 2.5 Flash Thinking' },
+    'gemini-2.0-flash': { name: 'Gemini 2.0 Flash' },
     'gemini-2.5-flash': { name: 'Gemini 2.5 Flash' },
-    'gemini-2.5-flash-lite': { name: 'Gemini 2.5 Flash Lite' }
+    'gemini-2.5-pro': { name: 'Gemini 2.5 Pro' },
+    'gemini-3-flash-preview': { name: 'Gemini 3 Flash Preview' },
+    'gemini-3-pro-preview': { name: 'Gemini 3 Pro Preview' }
+  }
+
+  const antigravityGeminiModels = {
+    'gemini-2.5-flash': { name: 'Gemini 2.5 Flash' },
+    'gemini-2.5-flash-lite': { name: 'Gemini 2.5 Flash Lite' },
+    'gemini-2.5-flash-thinking': { name: 'Gemini 2.5 Flash Thinking' },
+    'gemini-3-flash': { name: 'Gemini 3 Flash' },
+    'gemini-3-pro-low': { name: 'Gemini 3 Pro Low' },
+    'gemini-3-pro-high': { name: 'Gemini 3 Pro High' },
+    'gemini-3-pro-preview': { name: 'Gemini 3 Pro Preview' },
+    'gemini-3-pro-image': { name: 'Gemini 3 Pro Image' }
   }
   const claudeModels = {
     'claude-opus-4-5-thinking': { name: 'Claude Opus 4.5 Thinking' },
@@ -575,7 +583,7 @@ function generateOpenCodeConfig(platform: string, baseUrl: string, apiKey: strin
   } else if (platform === 'antigravity-gemini') {
     provider[platform].npm = '@ai-sdk/google'
     provider[platform].name = 'Antigravity (Gemini)'
-    provider[platform].models = geminiModels
+    provider[platform].models = antigravityGeminiModels
   } else if (platform === 'openai') {
     provider[platform].models = openaiModels
   }