Add dark workbench dashboard with host CPU/memory gauges.

Sample Windows CPU via Processor Utility so values match Task Manager, and expose host metrics on /v1/metrics/json for the workbench poll.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/test_host_metrics.py

@@ -0,0 +1,38 @@
+"""Host CPU/memory metrics (Windows + Linux)."""
+
+from __future__ import annotations
+
+import unittest
+from unittest.mock import patch
+
+import netx_api.host_metrics as host_metrics
+from netx_api.host_metrics import collect_host_metrics
+
+
+class HostMetricsTests(unittest.TestCase):
+    def setUp(self) -> None:
+        host_metrics._CACHED_HOST = None
+        host_metrics._CACHED_AT = 0.0
+
+    def test_collect_returns_cpu_mem_fields(self) -> None:
+        out = collect_host_metrics()
+        src = str(out.get("source") or "")
+        self.assertTrue(src.startswith("psutil") or src in {"stdlib", "error"}, src)
+        self.assertIn("cpu_percent", out)
+        self.assertIn("mem_percent", out)
+        self.assertGreaterEqual(float(out["cpu_percent"]), 0.0)
+        self.assertLessEqual(float(out["cpu_percent"]), 100.0)
+        self.assertGreaterEqual(float(out["mem_percent"]), 0.0)
+        self.assertLessEqual(float(out["mem_percent"]), 100.0)
+        self.assertGreaterEqual(int(out.get("mem_total_bytes") or 0), 0)
+
+    def test_stdlib_fallback_when_psutil_missing(self) -> None:
+        with patch("netx_api.host_metrics._host_via_psutil", return_value=None):
+            out = collect_host_metrics()
+        self.assertEqual(out.get("source"), "stdlib")
+        self.assertIn("cpu_percent", out)
+        self.assertIn("mem_percent", out)
+
+
+if __name__ == "__main__":
+    unittest.main()