fix: stop grouping HF/ModelScope models by repository

A repository is not a model identity: collection repos on Hugging Face
and ModelScope host many unrelated models, which were wrongly shown as
versions of each other.

- Hugging Face models no longer auto-group (the Hub exposes no
  site-native model id)
- ModelScope models group by the site's native published-model id
  (MuseInfo modelVersion.modelId), extracted during enrichment and
  persisted on the sidecar as source_model_id/source_version_id;
  unenriched models stay standalone instead of collapsing a whole repo
  into one group
- TensorArt grouping unchanged (its URL id is already model-level)
- Frontend group-key derivation mirrors the new backend semantics

tests/services/test_base_model_service.py

@@ -1263,39 +1263,8 @@ async def test_get_model_civitai_url_falls_back_when_host_setting_is_not_a_strin
     }
 
 
-class TestHfGroupKey:
-    """Tests for _extract_hf_group_key and _extract_group_key."""
-
-    # --- _extract_hf_group_key ---
-
-    def test_hf_group_key_valid_url(self):
-        """Standard HF URL returns hf:user/repo."""
-        item = {"hf_url": "https://huggingface.co/unsloth/qwen-edit"}
-        assert BaseModelService._extract_hf_group_key(item) == "hf:unsloth/qwen-edit"
-
-    def test_hf_group_key_url_with_subpath(self):
-        """URL with subpath still extracts just owner/repo."""
-        item = {"hf_url": "https://huggingface.co/user/repo/resolve/main/file.safetensors"}
-        assert BaseModelService._extract_hf_group_key(item) == "hf:user/repo"
-
-    def test_hf_group_key_empty_url(self):
-        """Empty hf_url returns None."""
-        assert BaseModelService._extract_hf_group_key({"hf_url": ""}) is None
-
-    def test_hf_group_key_no_url(self):
-        """Missing hf_url key returns None."""
-        assert BaseModelService._extract_hf_group_key({}) is None
-
-    def test_hf_group_key_none_url(self):
-        """None hf_url returns None."""
-        assert BaseModelService._extract_hf_group_key({"hf_url": None}) is None
-
-    def test_hf_group_key_invalid_url(self):
-        """Malformed HF URL returns None."""
-        assert BaseModelService._extract_hf_group_key({"hf_url": "not-a-url"}) is None
-        assert BaseModelService._extract_hf_group_key({"hf_url": "https://example.com"}) is None
-
-    # --- _extract_group_key ---
+class TestSourceGroupKey:
+    """Tests for _extract_group_key (CivitAI id, then site-native source identity)."""
 
     def test_group_key_civitai_only(self):
         """CivitAI modelId returned as int."""
@@ -1303,30 +1272,64 @@ class TestHfGroupKey:
         assert BaseModelService._extract_group_key(item) == 123
 
     def test_group_key_hf_only(self):
-        """HF-only item returns hf:user/repo string."""
+        """HF-linked items never group: a repository is not a model identity."""
         item = {"hf_url": "https://huggingface.co/user/repo"}
-        assert BaseModelService._extract_group_key(item) == "hf:user/repo"
+        assert BaseModelService._extract_group_key(item) is None
 
     def test_group_key_civitai_preferred(self):
-        """CivitAI modelId takes precedence over hf_url."""
+        """CivitAI modelId takes precedence over any source identity."""
         item = {
             "civitai": {"modelId": 456},
-            "hf_url": "https://huggingface.co/other/repo",
+            "source_url": "https://tensor.art/models/789",
         }
         assert BaseModelService._extract_group_key(item) == 456
 
     def test_group_key_neither(self):
-        """No CivitAI or HF returns None."""
+        """No CivitAI or groupable source returns None."""
         assert BaseModelService._extract_group_key({}) is None
         assert BaseModelService._extract_group_key({"some": "data"}) is None
 
     def test_group_key_civitai_none_model_id(self):
-        """civitai.modelId=None falls through to HF."""
+        """civitai.modelId=None falls through to the source identity."""
         item = {
             "civitai": {"modelId": None},
-            "hf_url": "https://huggingface.co/user/repo",
+            "source_url": "https://tensor.art/models/789",
         }
-        assert BaseModelService._extract_group_key(item) == "hf:user/repo"
+        assert BaseModelService._extract_group_key(item) == "ta:789"
+
+    def test_group_key_modelscope_uses_published_model_id(self):
+        """ModelScope groups under ms:<modelId> once enrichment recorded it."""
+        item = {
+            "source_platform": "modelscope",
+            "source_url": "https://modelscope.cn/models/u/r",
+            "source_model_id": "555",
+        }
+        assert BaseModelService._extract_group_key(item) == "ms:555"
+
+    def test_group_key_modelscope_unenriched_stays_standalone(self):
+        """Without source_model_id there is no key — never repo-level grouping."""
+        item = {
+            "source_platform": "modelscope",
+            "source_url": "https://modelscope.cn/models/u/r",
+        }
+        assert BaseModelService._extract_group_key(item) is None
+
+    def test_group_key_modelscope_identity_crosses_repos(self):
+        """Same published-model id groups across repos; same repo does not."""
+
+        def ms_item(repo, model_id):
+            return {
+                "source_platform": "modelscope",
+                "source_url": f"https://modelscope.cn/models/{repo}",
+                "source_model_id": model_id,
+            }
+
+        assert BaseModelService._extract_group_key(
+            ms_item("alice/collection", "555")
+        ) == BaseModelService._extract_group_key(ms_item("bob/mirror", "555"))
+        assert BaseModelService._extract_group_key(
+            ms_item("alice/collection", "555")
+        ) != BaseModelService._extract_group_key(ms_item("alice/collection", "777"))
 
 
 class TestApplyHashFilters: