图生 3D 的引用类型判别改用枚举

- server-rs/crates/api-server/src/tripo3d/image_source.rs：ResolvedReference.kind 从 &'static str 改成 ResolvedReferenceKind 枚举，From<EditorReferenceRecord> 写值与匹配比较由同一处产出，字符串错字不再只在运行期暴露
- server-rs/crates/api-server/src/tripo3d/image_source.rs：对外文案仍由 as_str() 生成，用例同步改用枚举取值

server-rs/crates/api-server/src/tripo3d/image_source.rs

@@ -87,19 +87,38 @@ async fn resolve_source_object_key(
 
 /// 定点查询返回的窄结果：只保留判定引用是否可用所需的记录类型与对象键。
 struct ResolvedReference {
-    kind: &'static str,
+    kind: ResolvedReferenceKind,
     object_key: Option<String>,
 }
 
+/// 记录类型判别：与 `Model3dGenerationSource` 的两个分支一一对应。
+///
+/// 用枚举而不是字符串字面量：`From<EditorReferenceRecord>` 写入的取值与
+/// `resolve_source_object_key_with` 里比较的取值由同一处产出，错字不会再拖到运行期才发现。
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+enum ResolvedReferenceKind {
+    Resource,
+    Asset,
+}
+
+impl ResolvedReferenceKind {
+    const fn as_str(self) -> &'static str {
+        match self {
+            Self::Resource => "resource",
+            Self::Asset => "asset",
+        }
+    }
+}
+
 impl From<EditorReferenceRecord> for ResolvedReference {
     fn from(record: EditorReferenceRecord) -> Self {
         match record {
             EditorReferenceRecord::ProjectResource(resource) => Self {
-                kind: "resource",
+                kind: ResolvedReferenceKind::Resource,
                 object_key: resource.object_key,
             },
             EditorReferenceRecord::Asset(asset) => Self {
-                kind: "asset",
+                kind: ResolvedReferenceKind::Asset,
                 object_key: asset.object_key,
             },
         }
@@ -119,8 +138,12 @@ where
     Fut: std::future::Future<Output = Result<ResolvedReference, AppError>>,
 {
     let (requested_kind, reference_id) = match source {
-        Model3dGenerationSource::Resource { resource_id } => ("resource", resource_id.as_str()),
-        Model3dGenerationSource::Asset { asset_id } => ("asset", asset_id.as_str()),
+        Model3dGenerationSource::Resource { resource_id } => {
+            (ResolvedReferenceKind::Resource, resource_id.as_str())
+        }
+        Model3dGenerationSource::Asset { asset_id } => {
+            (ResolvedReferenceKind::Asset, asset_id.as_str())
+        }
     };
     let resolved = resolve(reference_id.to_string()).await.map_err(|error| {
         // 只有「未登记（404）/ 引用非法（400）」这一类才是“引用不可用”，收敛成同一句 400；
@@ -132,7 +155,10 @@ where
         }
     })?;
     if resolved.kind != requested_kind {
-        return Err(image_source_kind_mismatch(requested_kind, resolved.kind));
+        return Err(image_source_kind_mismatch(
+            requested_kind.as_str(),
+            resolved.kind.as_str(),
+        ));
     }
     resolved
         .object_key
@@ -190,7 +216,7 @@ mod tests {
         AppError::from_status(status).with_details(json!({ "reason": "probe" }))
     }
 
-    fn resolved(kind: &'static str, object_key: Option<&str>) -> ResolvedReference {
+    fn resolved(kind: ResolvedReferenceKind, object_key: Option<&str>) -> ResolvedReference {
         ResolvedReference {
             kind,
             object_key: object_key.map(str::to_string),
@@ -207,7 +233,7 @@ mod tests {
                     resource_id: "res-1".to_string(),
                 },
                 "res-1",
-                "resource",
+                ResolvedReferenceKind::Resource,
                 "objects/res-1.png",
             ),
             (
@@ -215,7 +241,7 @@ mod tests {
                     asset_id: "asset-9".to_string(),
                 },
                 "asset-9",
-                "asset",
+                ResolvedReferenceKind::Asset,
                 "objects/asset-9.png",
             ),
         ] {
@@ -241,7 +267,10 @@ mod tests {
         };
 
         let error = resolve_source_object_key_with(&source, |_| async {
-            Ok(resolved("resource", Some("objects/asset-1.png")))
+            Ok(resolved(
+                ResolvedReferenceKind::Resource,
+                Some("objects/asset-1.png"),
+            ))
         })
         .await
         .expect_err("素材 ID 指向画布资源时必须报错");
@@ -264,10 +293,11 @@ mod tests {
             resource_id: "res-1".to_string(),
         };
 
-        let error =
-            resolve_source_object_key_with(&source, |_| async { Ok(resolved("resource", None)) })
-                .await
-                .expect_err("缺对象键时必须按服务端问题处理");
+        let error = resolve_source_object_key_with(&source, |_| async {
+            Ok(resolved(ResolvedReferenceKind::Resource, None))
+        })
+        .await
+        .expect_err("缺对象键时必须按服务端问题处理");
 
         assert_eq!(error.status_code(), StatusCode::BAD_GATEWAY);
         assert_eq!(