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

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

roundtable/alerts/routes.py

@@ -22,6 +22,10 @@ METRIC_CATALOG: dict[str, list[str]] = {
     "unifi":   ["is_up", "latency_ms", "total_clients"],
     "docker":  ["cpu_pct", "mem_pct"],
     "http":    ["is_up", "response_ms"],
+    "host_agent": [
+        "cpu_pct", "mem_used_pct", "mem_available_bytes", "swap_used_bytes",
+        "disk_used_pct_worst", "load_1m", "load_5m", "load_15m", "uptime_secs",
+    ],
     # snmp metrics are user-defined OID labels — populated dynamically from plugin_metrics
     "snmp":    [],
 }

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"},
+                ],
+            },
+        ],
+    },
 }