fix(ansible): surface run failure reason; widget audit cleanup

Run UX: when start_run throws before/around launch (e.g. ENOSPC creating the
temp dir — the box is out of disk), the run was marked "failed" with empty
output. Now the exception is broadcast + written to the run output/results so
the run view shows e.g. "[run error] OSError: [Errno 28] No space left on
device" instead of a blank failure.

Widget audit follow-ups (no broken links were found; these are consistency):
- host_resource_history widget now charts root (/) disk, consistent with the
  host panel (was the opaque "disk worst").
- host_resources widget: tooltip on the health dot explaining it warns on the
  worst mount while the number shows root.
- status_overview widget detail_url /status → /status/ (avoid redirect).
- Normalize ad-hoc widget empty-states to the shared .empty style (wording,
  which distinguishes "configured" vs "data yet", preserved).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plugins/host_agent/routes.py

@@ -398,16 +398,21 @@ async def widget_history():
         points = (await session.execute(
             select(PluginMetric).where(
                 PluginMetric.source_module == SOURCE_MODULE,
-                PluginMetric.resource_name == host.name,
-                PluginMetric.metric_name.in_(
-                    ("cpu_pct", "mem_used_pct", "disk_used_pct_worst")),
                 PluginMetric.recorded_at >= cutoff,
+                or_(
+                    and_(PluginMetric.resource_name == host.name,
+                         PluginMetric.metric_name.in_(("cpu_pct", "mem_used_pct"))),
+                    and_(PluginMetric.resource_name == host.name + ":/",
+                         PluginMetric.metric_name == "disk_used_pct"),
+                ),
             ).order_by(PluginMetric.recorded_at)
         )).scalars().all()
 
-    series: dict[str, list[dict]] = {"cpu_pct": [], "mem_used_pct": [], "disk_used_pct_worst": []}
+    # Disk = root (/), consistent with the host panel — not the opaque "worst".
+    series: dict[str, list[dict]] = {"cpu_pct": [], "mem_used_pct": [], "disk_root": []}
     for p in points:
-        series[p.metric_name].append({"t": p.recorded_at.isoformat(), "v": p.value})
+        key = "disk_root" if p.resource_name != host.name else p.metric_name
+        series[key].append({"t": p.recorded_at.isoformat(), "v": p.value})
 
     return await render_template("widget_history.html", host=host, series=series, hours=hours)