feat(dashboard): phase A widget clarity — threshold colours, host links, tooltips

Milestone 72 phase A (clarity wins, no schema change):
- Add shared metric_style() macro in _macros.html: colours a numeric metric
  amber (>=warn) / red (>=crit) on the value ITSELF, not just the status dot.
  Defaults 80/90 for percentage gauges; load /core uses warn 80 / crit 100.
  Applied to CPU/mem/disk across host_agent panel + fleet widget + the unified
  hosts-overview widget.
- Link every host reference to the host hub (/hosts/<id>) in ping, dns,
  hosts-overview, host_agent fleet, and uptime widgets; status widget entries
  link to their own detail_url. All guarded on session.user_id so the public
  share view degrades to plain text (the bare href carries no share token).
- Fix truncation: title= tooltips on all names that ellipsis, plus a hover
  underline affordance on the now-clickable ping-name links.

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

plugins/host_agent/templates/panel.html

@@ -1,4 +1,5 @@
 {# Per-host agent panel — embedded into /hosts/<id> via HTMX. Self-contained. #}
+{% from "_macros.html" import metric_style %}
 {% set scope = "steward:target:" ~ target.id if target else "" %}
 <div class="card">
   <div style="display:flex;align-items:baseline;justify-content:space-between;margin-bottom:0.75rem;gap:1rem;flex-wrap:wrap;">
@@ -21,19 +22,20 @@
   <div style="display:flex;gap:1.5rem;flex-wrap:wrap;margin-bottom:0.6rem;">
     <div title="Average CPU utilization across all cores">
       <div style="{{ lbl }}">CPU</div>
-      <div style="font-weight:600;">{{ '%.0f%%'|format(cpu) if cpu is not none else '—' }}</div>
+      <div style="font-weight:600;{{ metric_style(cpu) }}">{{ '%.0f%%'|format(cpu) if cpu is not none else '—' }}</div>
       {{ sparks.cpu | safe }}</div>
     <div title="RAM in use (total minus available; cache/buffers count as free)">
       <div style="{{ lbl }}">Memory</div>
-      <div style="font-weight:600;">{{ '%.0f%%'|format(mem) if mem is not none else '—' }}</div>
+      <div style="font-weight:600;{{ metric_style(mem) }}">{{ '%.0f%%'|format(mem) if mem is not none else '—' }}</div>
       {{ sparks.mem | safe }}</div>
     <div title="Root filesystem (/) usage — see Full metrics for every mount">
       <div style="{{ lbl }}">Disk /</div>
-      <div style="font-weight:600;">{{ '%.0f%%'|format(disk_root) if disk_root is not none else '—' }}</div>
+      <div style="font-weight:600;{{ metric_style(disk_root) }}">{{ '%.0f%%'|format(disk_root) if disk_root is not none else '—' }}</div>
       {{ sparks.disk | safe }}</div>
+    {# Load /core: 100% = run queue matches CPU capacity, so warn 80 / crit 100. #}
     <div title="1-minute load average ÷ {{ cores or '?' }} CPU cores (100% = run queue matches capacity). Raw 1m load: {{ '%.2f'|format(load1) if load1 is not none else '—' }}.">
       <div style="{{ lbl }}">Load /core</div>
-      <div style="font-weight:600;">{{ '%d%%'|format(load_per_core) if load_per_core is not none else ('%.2f'|format(load1) if load1 is not none else '—') }}</div>
+      <div style="font-weight:600;{{ metric_style(load_per_core, warn=80, crit=100) }}">{{ '%d%%'|format(load_per_core) if load_per_core is not none else ('%.2f'|format(load1) if load1 is not none else '—') }}</div>
       {{ sparks.load | safe }}</div>
   </div>
   {% if psi.cpu is not none or psi.mem is not none or psi.io is not none %}

plugins/host_agent/templates/widget_table.html

@@ -1,4 +1,5 @@
 {# host_agent widget — fleet glance, flex rows (no header wrap) #}
+{% from "_macros.html" import metric_style %}
 {% if rows %}
 <div style="display:grid;gap:0.1rem;">
   {% for r in rows %}
@@ -6,19 +7,21 @@
   <div style="display:flex;align-items:center;gap:0.6rem;font-size:0.82rem;padding:0.3rem 0;border-bottom:1px solid var(--border);">
     <span class="dot {% if stale %}dot-dim{% elif (r.cpu_pct or 0) >= 90 or (r.mem_used_pct or 0) >= 90 or (r.disk_worst or 0) >= 90 %}dot-warn{% else %}dot-up{% endif %}"
           title="{% if stale %}stale / no recent data{% else %}warns at CPU/memory ≥90% or any disk mount ≥90% (the 'disk /' figure shows root only){% endif %}"></span>
-    <a href="/hosts/{{ r.host.id }}"
-       style="flex:1;min-width:0;white-space:nowrap;overflow:hidden;text-overflow:ellipsis;font-weight:500;">
-      {{ r.host.name }}
-    </a>
+    {% set name_style = "flex:1;min-width:0;white-space:nowrap;overflow:hidden;text-overflow:ellipsis;font-weight:500;" %}
+    {% if session.user_id %}
+    <a href="/hosts/{{ r.host.id }}" title="{{ r.host.name }}" style="{{ name_style }}">{{ r.host.name }}</a>
+    {% else %}
+    <span title="{{ r.host.name }}" style="{{ name_style }}">{{ r.host.name }}</span>
+    {% endif %}
     <span style="display:flex;gap:0.75rem;font-variant-numeric:tabular-nums;color:var(--text-muted);font-size:0.75rem;flex-shrink:0;">
       {% if r.cpu_pct is not none %}
-      <span title="CPU"><span style="color:var(--text-dim);">cpu</span> {{ "%.0f"|format(r.cpu_pct) }}%</span>
+      <span title="CPU" style="{{ metric_style(r.cpu_pct) }}"><span style="color:var(--text-dim);">cpu</span> {{ "%.0f"|format(r.cpu_pct) }}%</span>
       {% endif %}
       {% if r.mem_used_pct is not none %}
-      <span title="Memory"><span style="color:var(--text-dim);">mem</span> {{ "%.0f"|format(r.mem_used_pct) }}%</span>
+      <span title="Memory" style="{{ metric_style(r.mem_used_pct) }}"><span style="color:var(--text-dim);">mem</span> {{ "%.0f"|format(r.mem_used_pct) }}%</span>
       {% endif %}
       {% if r.disk_root is not none %}
-      <span title="Root filesystem (/) usage"><span style="color:var(--text-dim);">disk /</span> {{ "%.0f"|format(r.disk_root) }}%</span>
+      <span title="Root filesystem (/) usage" style="{{ metric_style(r.disk_root) }}"><span style="color:var(--text-dim);">disk /</span> {{ "%.0f"|format(r.disk_root) }}%</span>
       {% endif %}
       {% if r.load_1m is not none %}
       <span title="Load average 1m"><span style="color:var(--text-dim);">load</span> {{ "%.2f"|format(r.load_1m) }}</span>