fix: image model ranking crashes on a non-string search filter (#1898)

tests/test_image_models_nonstring_search.py

@@ -0,0 +1,15 @@
+from services.hwfit.image_models import rank_image_models, IMAGE_MODEL_REGISTRY
+
+SYS = {"gpu_vram_gb": 0, "has_gpu": False}
+
+
+def test_rank_image_models_handles_non_string_search():
+    # search is a CLI/API filter arg; a non-string made search.lower() raise
+    # AttributeError. A non-string search should behave as "no filter".
+    out = rank_image_models(SYS, search=123)
+    assert len(out) == len(IMAGE_MODEL_REGISTRY)
+
+
+def test_rank_image_models_string_filter_still_applies():
+    out = rank_image_models(SYS, search="zzzznotarealmodelzzz")
+    assert out == []