让 resolve_image_provider 的拒绝原因带上模型名

- resolve_image_provider 错误类型从 &'static str 改为 String，未知模型返回「不支持的图片模型：{model}」
- ensure_provider_matches_model 去掉重复拼接的模型名，避免错误信息出现两遍输入
- openai_image_generation 缺少参考图的本地校验改用显式 match，不再用 unwrap_or 静默假定 Tiantoken
- 补充断言：业务模型名与 unknown-model 的拒绝原因里必须包含被拒绝的模型值

server-rs/crates/api-server/src/openai_image_generation.rs

@@ -243,7 +243,12 @@ pub(crate) async fn create_openai_image_edit_with_references_and_model(
     // 中文注释：先做本地参考图校验，避免 provider 客户端缺失时在校验前 panic。
     // provider 归属与下方非空参考图路径保持一致，按模型解析而不是固定 Tiantoken。
     if reference_images.is_empty() {
-        let provider = resolve_image_provider(model).unwrap_or(ImageProvider::Tiantoken);
+        let provider = match resolve_image_provider(model) {
+            Ok(provider) => provider,
+            // 这里只为一个本地校验错误选归属标签；未知模型无法归属 provider 时
+            // 显式回落到 Tiantoken，不再用 unwrap_or 静默吞掉解析失败。
+            Err(_) => ImageProvider::Tiantoken,
+        };
         return map_platform_image_result(
             settings,
             Err(missing_reference_images_error(provider, failure_context)),

server-rs/crates/platform-image/src/image_provider/protocol/request.rs

@@ -120,13 +120,13 @@ pub(crate) fn normalize_nanobanana_model(model: &str) -> &str {
 /// nanobanana 走 VectorEngine。业务模型名 `gpt-image-2.5`
 /// (`GPT_IMAGE_2_5_BUSINESS_NAME`) 必须在任务边界解析成具体 key；已删除的
 /// `gpt-image-2-c` 命中即拒绝。`gpt-image-2` 仍按历史可读值接受。
-pub fn resolve_image_provider(model: &str) -> Result<ImageProvider, &'static str> {
+pub fn resolve_image_provider(model: &str) -> Result<ImageProvider, String> {
     match normalize_image_model(model) {
         GPT_IMAGE_2_MODEL | GPT_IMAGE_2_5_GENERATION_MODEL | GPT_IMAGE_2_5_EDIT_MODEL => {
             Ok(ImageProvider::Tiantoken)
         }
         NANOBANANA_2_MODEL => Ok(ImageProvider::VectorEngine),
-        _ => Err("不支持的图片模型"),
+        _ => Err(format!("不支持的图片模型：{model}")),
     }
 }
 

server-rs/crates/platform-image/src/image_provider/runtime/executor.rs

@@ -709,10 +709,11 @@ pub(crate) fn ensure_provider_matches_model(
     model: &str,
     failure_context: &str,
 ) -> Result<(), PlatformImageError> {
+    // `resolve_image_provider` 的错误信息已经带上被拒绝的模型名，这里不再重复拼接。
     let resolved =
         resolve_image_provider(model).map_err(|message| PlatformImageError::InvalidRequest {
             provider: settings.provider.as_str(),
-            message: format!("{failure_context}：{message}：{model}"),
+            message: format!("{failure_context}：{message}"),
         })?;
     if resolved != settings.provider {
         return Err(PlatformImageError::InvalidRequest {

server-rs/crates/platform-image/tests/image_provider.rs

@@ -220,7 +220,12 @@ fn nanobanana_generate_content_url_blank_model_falls_back_to_nanobanana_model()
 #[test]
 fn resolve_image_provider_rejects_business_model_and_accepts_concrete_models() {
     // 中文注释：业务模型名不是 provider model，必须在 api-server 任务边界先解析成具体 model。
-    assert!(resolve_image_provider(GPT_IMAGE_2_5_BUSINESS_NAME).is_err());
+    let business_model_error =
+        resolve_image_provider(GPT_IMAGE_2_5_BUSINESS_NAME).expect_err("业务模型名必须被拒绝");
+    assert!(
+        business_model_error.contains(GPT_IMAGE_2_5_BUSINESS_NAME),
+        "拒绝原因必须带上被拒绝的模型名，实际为：{business_model_error}"
+    );
     // 中文注释：已删除的 gpt-image-2-c 不再被任何层接受。
     assert!(resolve_image_provider("gpt-image-2-c").is_err());
 
@@ -242,7 +247,12 @@ fn resolve_image_provider_rejects_business_model_and_accepts_concrete_models() {
         resolve_image_provider("gemini-3.1-flash-image-preview"),
         Ok(ImageProvider::VectorEngine)
     );
-    assert!(resolve_image_provider("unknown-model").is_err());
+    let unknown_model_error =
+        resolve_image_provider("unknown-model").expect_err("未知模型必须被拒绝");
+    assert!(
+        unknown_model_error.contains("unknown-model"),
+        "拒绝原因必须带上被拒绝的模型名，实际为：{unknown_model_error}"
+    );
 }
 
 #[tokio::test]