fix(hwfit): normalize CPU arch for fallback estimates (#4441)

tests/test_hwfit_cpu_arch_detection.py

@@ -0,0 +1,55 @@
+"""CPU architecture normalization for HW Fit hardware detection."""
+
+import pytest
+
+from services.hwfit import hardware
+
+
+@pytest.fixture(autouse=True)
+def _clear_hwfit_cache(monkeypatch):
+    hardware._cache_by_host.clear()
+    monkeypatch.setattr(hardware, "_remote_host", None)
+    monkeypatch.setattr(hardware, "_remote_platform", None)
+    monkeypatch.setattr(hardware, "_is_containerized", lambda: False)
+    yield
+    hardware._cache_by_host.clear()
+
+
+def _stub_common_probe(monkeypatch, machine):
+    monkeypatch.setattr(hardware.platform, "machine", lambda: machine)
+    monkeypatch.setattr(hardware, "_get_ram_gb", lambda: 64.0)
+    monkeypatch.setattr(hardware, "_get_available_ram_gb", lambda: 48.0)
+    monkeypatch.setattr(hardware, "_get_cpu_count", lambda: 16)
+    monkeypatch.setattr(hardware, "_get_cpu_name", lambda: "Test CPU")
+    monkeypatch.setattr(hardware, "_detect_apple_silicon", lambda: None)
+    monkeypatch.setattr(hardware, "_detect_amd", lambda: None)
+
+
+def test_detect_system_reports_cpu_arch_for_gpu_backends(monkeypatch):
+    """GPU-backed systems still need CPU architecture for cpu_only estimates."""
+    _stub_common_probe(monkeypatch, "aarch64")
+    monkeypatch.setattr(hardware, "_detect_nvidia", lambda: {
+        "gpu_name": "NVIDIA GB10",
+        "gpu_vram_gb": 64.0,
+        "gpu_count": 1,
+        "gpus": [],
+        "gpu_groups": [],
+        "homogeneous": True,
+        "backend": "cuda",
+    })
+
+    system = hardware.detect_system(fresh=True)
+
+    assert system["backend"] == "cuda"
+    assert system["cpu_arch"] == "arm64"
+
+
+def test_detect_system_keeps_32_bit_arm_on_conservative_cpu_backend(monkeypatch):
+    """Plain arm/armv7 is not the same as the ARM64-class cpu_arm fallback."""
+    _stub_common_probe(monkeypatch, "armv7l")
+    monkeypatch.setattr(hardware, "_detect_nvidia", lambda: None)
+
+    system = hardware.detect_system(fresh=True)
+
+    assert system["cpu_arch"] == "arm"
+    assert system["backend"] == "cpu_x86"