fix(download): save multi-variant files under raw stored filenames (#1100)

The public REST API rewrites files[].name to "{model}_{version}" for
non-LoRA model types, so every precision variant of a multi-file version
shared one name and landed on disk with a random short-hash suffix.

Fetch the raw stored filename from the model-versions/mini endpoint
(always pinned with modelFileId) and use it for the on-disk name and
metadata when available; fall back silently to the REST name otherwise.
CivArchive already serves raw names and is skipped.

tests/services/test_model_metadata_provider.py

@@ -207,3 +207,62 @@ async def test_retry_helper_retries_normally_for_small_retry_after(monkeypatch):
     result, _ = await helper.run("test", succeeding)
     assert result == {"ok": True}
     assert calls == 2  # Retried once (small retry_after)
+
+
+class MiniCapableProvider(ModelMetadataProvider):
+    """Provider that serves raw file names via the mini endpoint (#1100)."""
+
+    def __init__(self, payload=None) -> None:
+        self.payload = payload
+        self.calls = []
+
+    async def get_model_by_hash(self, model_hash: str):
+        return None, None
+
+    async def get_model_versions(self, model_id: str):
+        return None
+
+    async def get_model_version(self, model_id=None, version_id=None):
+        return None
+
+    async def get_model_version_info(self, version_id: str):
+        return None, None
+
+    async def get_user_models(self, username: str, cursor=None):
+        return None
+
+    async def get_version_file_mini(self, version_id: int, file_id: int):
+        self.calls.append((version_id, file_id))
+        return self.payload
+
+
+@pytest.mark.asyncio
+async def test_base_provider_get_version_file_mini_defaults_to_none():
+    provider = TrackingProvider()
+    assert await provider.get_version_file_mini(1, 2) is None
+
+
+@pytest.mark.asyncio
+async def test_fallback_get_version_file_mini_returns_first_hit():
+    primary = TrackingProvider()  # base default: None
+    secondary = MiniCapableProvider({"fileName": "raw.safetensors"})
+
+    fallback = FallbackMetadataProvider(
+        [("primary", primary), ("secondary", secondary)],
+    )
+
+    result = await fallback.get_version_file_mini(10, 20)
+
+    assert result == {"fileName": "raw.safetensors"}
+    assert secondary.calls == [(10, 20)]
+
+
+@pytest.mark.asyncio
+async def test_rate_limit_retrying_provider_delegates_get_version_file_mini():
+    inner = MiniCapableProvider({"fileName": "raw.safetensors"})
+    wrapper = RateLimitRetryingProvider(inner, label="inner")
+
+    result = await wrapper.get_version_file_mini(10, 20)
+
+    assert result == {"fileName": "raw.safetensors"}
+    assert inner.calls == [(10, 20)]