ops: add disk capacity incident assessment

tests/test_disk_capacity.py

@@ -0,0 +1,19 @@
+from src.disk_capacity import assess_disk_capacity, read_disk_capacity
+
+
+def test_usage_at_incident_threshold_requires_action():
+    status = assess_disk_capacity(total_bytes=100, available_bytes=15)
+
+    assert status == {
+        "usage_percent": 85.0,
+        "threshold_percent": 85.0,
+        "incident": True,
+    }
+
+
+def test_read_disk_capacity_assesses_a_real_filesystem(tmp_path):
+    status = read_disk_capacity(tmp_path)
+
+    assert 0 <= status["usage_percent"] <= 100
+    assert status["threshold_percent"] == 85.0
+    assert status["incident"] is (status["usage_percent"] >= 85.0)