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_model_sources.py

@@ -279,15 +279,39 @@ class TestHelpers:
         assert get_source_platform({"source_platform": "tensorart"}) == "tensorart"
         assert get_source_platform({}) == ""
 
-    def test_group_keys_match_legacy_hf_shape(self):
-        assert source_group_key({"hf_url": "https://huggingface.co/u/r"}) == "hf:u/r"
-        assert (
-            source_group_key({"source_url": "https://modelscope.cn/models/u/r"}) == "ms:u/r"
-        )
+    def test_group_keys_use_site_native_identity(self):
+        # Hugging Face has no site-native model identity: never grouped.
+        assert source_group_key({"hf_url": "https://huggingface.co/u/r"}) is None
+        # TensorArt's numeric id already identifies a single model.
         assert (
             source_group_key({"source_url": "https://tensor.art/models/123"}) == "ta:123"
         )
 
+    def test_modelscope_groups_by_published_model_id(self):
+        # Without an enriched source_model_id the model stays standalone —
+        # never grouped by repo, which would collapse a collection repo.
+        assert (
+            source_group_key({"source_url": "https://modelscope.cn/models/u/r"}) is None
+        )
+        assert (
+            source_group_key(
+                {
+                    "source_url": "https://modelscope.cn/models/u/r",
+                    "source_model_id": "555",
+                }
+            )
+            == "ms:555"
+        )
+        assert (
+            source_group_key(
+                {
+                    "source_url": "https://www.modelscope.ai/models/u/r",
+                    "source_model_id": "678",
+                }
+            )
+            == "msai:678"
+        )
+
     def test_group_key_is_none_without_source(self):
         assert source_group_key({}) is None
         assert source_group_key({"hf_url": "https://example.com/x"}) is None
@@ -457,7 +481,12 @@ def _modelscope_detail_payload() -> dict:
                 "versions": [
                     {
                         "stats": {"fileList": ["Krea-2-LORA_c1-st8000.safetensors"]},
-                        "modelVersion": {"showName": "c1-st8000", "triggerWords": '[""]'},
+                        "modelVersion": {
+                            "showName": "c1-st8000",
+                            "triggerWords": '[""]',
+                            "id": 1001,
+                            "modelId": 555,
+                        },
                         "coverImages": [
                             {"url": "https://resources.modelscope.cn/cover-images/a.png"}
                         ],
@@ -467,6 +496,8 @@ def _modelscope_detail_payload() -> dict:
                         "modelVersion": {
                             "showName": "c1-st1000",
                             "triggerWords": '["kreaface","kreamodel"]',
+                            "id": 1002,
+                            "modelId": 555,
                         },
                         "coverImages": [
                             {"url": "https://resources.modelscope.cn/cover-images/b.png"},
@@ -533,6 +564,9 @@ class TestFetchModelCardContext:
         # The version label is taken from the file that was matched, not from
         # whichever version happens to come first in the payload.
         assert context.version_name == "c1-st1000"
+        # The site-native identity ids belong to the matched version too.
+        assert context.source_model_id == "555"
+        assert context.source_version_id == "1002"
 
     @pytest.mark.asyncio
     async def test_modelscope_version_label_is_empty_for_an_unknown_file(
@@ -550,6 +584,9 @@ class TestFetchModelCardContext:
         )
 
         assert context.version_name == ""
+        # No version matched, so there is no per-version identity either.
+        assert context.source_model_id == ""
+        assert context.source_version_id == ""
         # The repository-wide fields are still published.
         assert context.model_name == "Krea-2-LORA"