feat(host_agent): a disk out of inodes reads as full (#5745)

VDNT-Util01's / ran out of inodes (956 free of 60.8M) with 274G of space
left; every file create failed and Steward's page read healthy at 66%.

- Agent 1.13.0 reports each mount's inodes (statvfs; a filesystem reporting
  none, like btrfs, is left without).
- Ingest records inodes_used_pct per mount, and disk_used_pct_worst is the
  fullest mount by space or inodes, so existing disk-full rules and the
  overview see it.
- The host's health strip, the Hosts widget and the host glance grade / by
  whichever is fuller and name inodes when they are ("Disk / 66% · inodes
  100%", "Inodes on / ... past its critical threshold").

Hosts pick up the inode figures once their agent is updated to 1.13.0.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

steward/templates/hosts/overview_widget.html

@@ -33,7 +33,8 @@
     </td>
     {% for v, kind in ((a.get('cpu_pct'), 'cpu'), (a.get('mem_used_pct'), 'mem'), (a.get('disk_root'), 'disk')) %}
     {% set g = (r.grades or {}).get(kind) or (none, none) %}
-    <td style="{{ grade_style(g[0]) }}"{% if g[1] %} title="{{ g[1]|capitalize }}"{% endif %}>{% if v is none %}—{% else %}{{ "%.0f"|format(v) }}%{% endif %}</td>
+    {% set inodes = a.get('inodes_root') if kind == 'disk' else none %}
+    <td style="{{ grade_style(g[0]) }}"{% if g[1] %} title="{{ g[1]|capitalize }}"{% elif inodes is not none and (v is none or inodes > v) %} title="Inodes {{ '%.0f'|format(inodes) }}% used: no file can be created once they run out"{% endif %}>{% if v is none %}—{% else %}{{ "%.0f"|format(v) }}%{% endif %}{% if inodes is not none and (v is none or inodes > v) and inodes >= 80 %} <span class="w-sub">inodes {{ "%.0f"|format(inodes) }}%</span>{% endif %}</td>
     {% endfor %}
     {% set g = (r.grades or {}).get('load') or (none, none) %}
     <td style="{{ grade_style(g[0]) }}"