feat(host_agent): register widgets and alert metric catalog entry

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

roundtable/core/widgets.py

@@ -247,6 +247,38 @@ WIDGET_REGISTRY: dict[str, dict] = {
         "poll": True,
         "params": [],
     },
+    "host_resources": {
+        "key": "host_resources",
+        "label": "Host Agent — Resources",
+        "description": "Fleet view: CPU, memory, disk, and load per monitored host",
+        "hx_url": "/plugins/host_agent/widget",
+        "detail_url": "/plugins/host_agent/settings/",
+        "plugin": "host_agent",
+        "poll": True,
+        "params": [],
+    },
+    "host_resource_history": {
+        "key": "host_resource_history",
+        "label": "Host Agent — History",
+        "description": "CPU/memory/disk history for one host",
+        "hx_url": "/plugins/host_agent/widget/history",
+        "detail_url": "/plugins/host_agent/settings/",
+        "plugin": "host_agent",
+        "poll": True,
+        "params": [
+            {
+                "key": "hours",
+                "label": "Time range",
+                "type": "select",
+                "default": 6,
+                "options": [
+                    {"value": 1,  "label": "Last 1 hour"},
+                    {"value": 6,  "label": "Last 6 hours"},
+                    {"value": 24, "label": "Last 24 hours"},
+                ],
+            },
+        ],
+    },
 }