修正GT未知类别导入为待分类

- GT Mask 未知 maskid 选择保留时落到黑色 maskid:0 的待分类类别，而不是绿色未定义类别。

- 前端导入预览中未知 maskid 使用黑色待分类覆盖色，并把按钮文案改为导入为待分类。

- 待分类兜底颜色统一为 #000000，和模板保留类、GT_label/Pro_label 导出规则一致。

- 补充后端回归断言并更新 AGENTS 与文档说明，保留 gt_unknown_class 和原始 gt_label_value 供后续重命名追溯。

backend/routers/ai.py

@@ -43,6 +43,14 @@ GT_MASK_EMPTY_DETAIL = "GT Mask 图片中没有非背景 maskid 区域。"
 GT_IMPORT_MAX_CONTOUR_POINTS = 2048
 GT_IMPORT_CONTOUR_EPSILON_RATIO = 0.00075
 GT_IMPORT_MIN_CONTOUR_EPSILON = 0.35
+RESERVED_UNCLASSIFIED_CLASS = {
+    "id": "reserved-unclassified",
+    "name": "待分类",
+    "color": "#000000",
+    "zIndex": 0,
+    "maskId": 0,
+    "category": "系统保留",
+}
 
 
 def _shared_project_or_404(project_id: int, db: Session, current_user: User) -> Project:
@@ -107,10 +115,11 @@ def _rgb_tuple_to_hex(rgb: tuple[int, int, int]) -> str:
     return f"#{values[0]:02x}{values[1]:02x}{values[2]:02x}"
 
 
-def _template_class_maps(template: Template | None) -> tuple[dict[int, dict[str, Any]], dict[str, dict[str, Any]]]:
+def _template_class_maps(template: Template | None) -> tuple[dict[int, dict[str, Any]], dict[str, dict[str, Any]], dict[str, Any]]:
     classes = ((template.mapping_rules or {}).get("classes") if template else None) or []
     by_maskid: dict[int, dict[str, Any]] = {}
     by_color: dict[str, dict[str, Any]] = {}
+    unclassified = dict(RESERVED_UNCLASSIFIED_CLASS)
     for index, item in enumerate(classes):
         if not isinstance(item, dict):
             continue
@@ -128,16 +137,13 @@ def _template_class_maps(template: Template | None) -> tuple[dict[int, dict[str,
             "maskId": maskid,
             **({"category": item.get("category")} if item.get("category") else {}),
         }
+        if maskid == 0 or class_meta["id"] == RESERVED_UNCLASSIFIED_CLASS["id"] or class_meta["name"] == RESERVED_UNCLASSIFIED_CLASS["name"]:
+            unclassified = dict(RESERVED_UNCLASSIFIED_CLASS)
+            continue
         if maskid > 0:
             by_maskid[maskid] = class_meta
         by_color[color] = class_meta
-    return by_maskid, by_color
-
-
-def _gt_unknown_label(token: int | str) -> str:
-    if isinstance(token, int):
-        return f"未定义类别 {token}"
-    return f"未定义颜色 {token}"
+    return by_maskid, by_color, unclassified
 
 
 def _load_frame_image(frame: Frame) -> np.ndarray:
@@ -1048,7 +1054,7 @@ async def import_gt_mask(
     if resized_to_frame:
         label_image = cv2.resize(label_image, (width, height), interpolation=cv2.INTER_NEAREST)
 
-    by_maskid, _by_color = _template_class_maps(template)
+    by_maskid, _by_color, unclassified_class = _template_class_maps(template)
     has_template_classes = bool(by_maskid)
     fallback_color = _normalize_hex_color(color) or "#22c55e"
 
@@ -1065,8 +1071,9 @@ async def import_gt_mask(
             annotation_label = class_meta["name"]
             annotation_color = class_meta["color"]
         elif is_unknown:
-            annotation_label = _gt_unknown_label(label_value)
-            annotation_color = fallback_color
+            annotation_label = unclassified_class["name"]
+            annotation_color = unclassified_class["color"]
+            class_meta = unclassified_class
         else:
             annotation_label = f"{label} {label_value}" if len(label_values) > 1 else label
             annotation_color = fallback_color

backend/tests/test_ai.py

@@ -1664,8 +1664,17 @@ def test_import_gt_mask_handles_unknown_maskid_policy_and_resizes_to_frame(clien
 
     assert undefined_response.status_code == 201
     labels = {item["mask_data"]["label"] for item in undefined_response.json()}
-    assert labels == {"已定义", "未定义类别 2"}
-    unknown = next(item for item in undefined_response.json() if item["mask_data"]["label"].startswith("未定义"))
+    assert labels == {"已定义", "待分类"}
+    unknown = next(item for item in undefined_response.json() if item["mask_data"]["label"] == "待分类")
+    assert unknown["mask_data"]["color"] == "#000000"
+    assert unknown["mask_data"]["class"] == {
+        "id": "reserved-unclassified",
+        "name": "待分类",
+        "color": "#000000",
+        "zIndex": 0,
+        "maskId": 0,
+        "category": "系统保留",
+    }
     assert unknown["mask_data"]["gt_unknown_class"] is True
     assert unknown["mask_data"]["gt_label_value"] == 2
     assert unknown["mask_data"]["gt_resized_to_frame"] is True