fix: verify model generation and retain credentials

Save and test could accept a successful endpoint response without proving that the selected model generated output, while changing a connection URL or temporarily disabling authentication could require the API Key again.

Model tests now issue bounded real text or image generation requests and validate their output. API Keys remain encrypted with their connection across URL and authentication changes until explicitly cleared or the connection is deleted, and the form places the key directly below authentication. Real tests may incur a small amount of provider usage.

Release note: 修复模型“保存并测试”仅验证连通性的问题；现在会执行真实文本或图片生成测试，并在修改地址或临时关闭认证时继续保留该连接的加密 API Key。

src/main/agent/model-runtime.ts

@@ -1640,6 +1640,18 @@ export class ModelAgentRuntime implements AgentRuntime {
     return headers
   }
 
+  private createImageGenerationRequest(
+    prompt: string
+  ): Record<string, unknown> {
+    return {
+      model: this.options.model,
+      prompt: prompt.slice(0, 100_000),
+      n: 1,
+      quality: this.options.imageGenerationQuality ?? 'auto',
+      response_format: 'b64_json'
+    }
+  }
+
   private async fetchWithTimeout(
     input: URL,
     init: RequestInit,
@@ -1688,38 +1700,44 @@ export class ModelAgentRuntime implements AgentRuntime {
     if (!this.isConfigured()) {
       return this.getStatus()
     }
-    if (this.options.protocol === 'openai-images-generations') {
-      return {
-        ...(await this.getStatus()),
-        detail: `已识别图像生成配置，发送提示词时执行实际生成验证 · ${this.options.baseUrl}`
-      }
-    }
+    const imageGeneration =
+      this.options.protocol === 'openai-images-generations'
+    const marker = `GOODBUDDY_MODEL_TEST_${randomBytes(12)
+      .toString('hex')
+      .toUpperCase()}`
+    const prompt = imageGeneration
+      ? 'Generate a simple image of one solid blue circle centered on a white background.'
+      : `Reply with exactly this text and nothing else: ${marker}`
     const response = await this.fetcher(this.getEndpoint(), {
       method: 'POST',
-      signal: AbortSignal.timeout(30_000),
+      signal: AbortSignal.timeout(60_000),
       headers: this.getHeaders(),
       body: JSON.stringify(
-        this.options.protocol === 'openai-responses'
+        imageGeneration
+          ? this.createImageGenerationRequest(prompt)
+          : this.options.protocol === 'openai-responses'
           ? {
               model: this.options.model,
-              max_output_tokens: 16,
+              max_output_tokens: 64,
               stream: false,
-              input: 'Reply OK.'
+              input: prompt
             }
           : {
               model: this.options.model,
-              max_tokens: 1,
+              max_tokens: 64,
               stream: false,
-              messages: [{ role: 'user', content: 'Reply OK.' }]
+              messages: [{ role: 'user', content: prompt }]
             }
       )
     })
+    const responseText = await readBoundedResponseText(response, {
+      maxBytes: response.ok && imageGeneration
+        ? maxImageResponseBytes
+        : 128 * 1024,
+      missingBodyMessage: '模型接口未返回响应内容',
+      tooLargeMessage: '模型接口响应超过安全限制'
+    })
     if (!response.ok) {
-      const responseText = await readBoundedResponseText(response, {
-        maxBytes: 128 * 1024,
-        missingBodyMessage: '模型接口未返回响应内容',
-        tooLargeMessage: '模型接口响应超过安全限制'
-      })
       let detail: string | undefined
       try {
         detail = getErrorMessage(
@@ -1733,13 +1751,34 @@ export class ModelAgentRuntime implements AgentRuntime {
           `模型接口连接测试失败（HTTP ${response.status}）`
       )
     }
-    await response.body?.cancel().catch(() => undefined)
+    let payload: unknown
+    try {
+      payload = JSON.parse(responseText)
+    } catch {
+      throw new Error('模型接口返回了无效 JSON，未完成真实生成测试')
+    }
+    if (imageGeneration) {
+      parseGeneratedImage(payload)
+    } else {
+      const result = parseModelToolResponse(
+        payload,
+        this.options.protocol === 'anthropic-messages'
+          ? 'anthropic'
+          : this.options.protocol === 'openai-responses'
+            ? 'openai-responses'
+            : 'openai'
+      )
+      if (!result.text.includes(marker)) {
+        throw new Error('模型接口未返回测试文本，未完成真实生成测试')
+      }
+    }
     return {
-      id: 'model',
-      label: this.options.model,
+      ...(await this.getStatus()),
       available: true,
-      supportsToolExecution: this.supportsToolExecution,
-      detail: `已验证模型接口连接 · ${this.options.baseUrl}`
+      detail: `${imageGeneration
+        ? '已完成真实图像生成测试'
+        : '已完成真实模型生成测试'
+      } · ${this.options.baseUrl}`
     }
   }
 
@@ -2376,13 +2415,9 @@ export class ModelAgentRuntime implements AgentRuntime {
       type: 'status',
       message: `${this.options.model} 正在生成图片`
     }
-    const imageRequest = {
-      model: this.options.model,
-      prompt: request.prompt.slice(0, 100_000),
-      n: 1,
-      quality: this.options.imageGenerationQuality ?? 'auto',
-      response_format: 'b64_json'
-    }
+    const imageRequest = this.createImageGenerationRequest(
+      request.prompt
+    )
     const modelRequest = await this.fetchWithTimeout(
       this.getEndpoint(),
       {