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/docker/templates/docker/widget.html

@@ -1,6 +1,6 @@
 {# docker/widget.html — dashboard widget: container status overview #}
 {% if not containers and running_count == 0 and stopped_count == 0 %}
-<div style="color:var(--text-muted);font-size:0.85rem;padding:0.5rem 0;">No containers found.</div>
+<p class="empty" style="padding:0.5rem 0;font-size:0.85rem;">No containers found.</p>
 {% else %}
 
 <div style="display:flex;gap:1rem;margin-bottom:0.65rem;">