feat(hosts): the live strip shows the hottest sensor's temperature, get_host marks sensors that don't count, and the Monitors card's button reads "Add" (#6803)

- The host page's live strip gains a Temperature tile: temp_c_max (real
  thermometers only), its last 6 h and the sensor setting it, graded by
  Settings → Thresholds and counted in the header's worst reading, in °C.
- MCP get_host: each temperature carries `counted`; an unwired input is
  `counted: false` with `not_counted_because`, listed after the real ones.
  host_agent registers the judge (judge_sensors), so core imports no plugin.
- The Monitors card's "Add monitor" wrapped into two lines beside the
  uptime; it reads "Add", titled "Add a monitor for this host".

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

plugins/host_agent/templates/_host_vitals.html

@@ -1,10 +1,11 @@
 {# Host health header — live polled into the host hub: live or stale, the worst
    reading against Settings → Thresholds, last seen, then CPU / memory / disk /
-   load tiles graded by the same cutoffs (`grades`; CPU, memory and load within
+   load tiles, and the hottest sensor that counts with its name, graded by the same cutoffs (`grades`; CPU, memory and load within
    the host's own normal for the hour read healthy, and `usual` says so). Renders nothing until the agent
    reports (the Agent panel below then shows provisioning). #}
 {% from "_macros.html" import status_badge, stat_tile %}
 {% macro pct(v) %}{{ '%.0f%%'|format(v) if v is not none else '—' }}{% endmacro %}
+{% macro deg(v) %}{{ '%.0f°C'|format(v) if v is not none else '—' }}{% endmacro %}
 {% set grades = grades or {} %}
 {% if reporting %}
 <section class="card host-health" aria-label="Host health">
@@ -12,7 +13,7 @@
     {{ status_badge('stale' if stale else 'up', 'Stale' if stale else 'Live') }}
     <span class="host-health-summary">
       {%- if stale %}No report since {{ reg.last_seen_at|ago }}; the readings below are from then.
-      {%- elif worst %}<span class="tone-{{ worst[2] }}">{{ worst[0] }} {{ pct(worst[1]) }}</span> is past its {{ "critical" if worst[2] == "crit" else "warning" }} threshold.
+      {%- elif worst %}<span class="tone-{{ worst[2] }}">{{ worst[0] }} {{ deg(worst[1]) if worst[0] == "Temperature" else pct(worst[1]) }}</span> is past its {{ "critical" if worst[2] == "crit" else "warning" }} threshold.
       {%- elif usual %}Every reading is within its thresholds or its usual level for this hour.
       {%- else %}Every reading is within its thresholds.{% endif -%}
     </span>
@@ -24,13 +25,17 @@
     {# Charts, every mount, interface, disk and temperature sensor. #}
     <a href="/plugins/host_agent/{{ reg.host_id }}/" class="btn btn-sm btn-ghost" style="margin-left:auto;">Full metrics →</a>
   </div>
-  <div class="stat-strip host-health-tiles" style="margin-bottom:0;">
+  <div class="stat-strip host-health-tiles" style="margin-bottom:0;--tiles:{{ 5 if temp is not none else 4 }};">
     {{ stat_tile("CPU", pct(cpu), state=(grades.cpu or [status_class(cpu, 'cpu')])[0], hint=sparks.cpu|safe) }}
     {{ stat_tile("Memory", pct(mem), state=(grades.mem or [status_class(mem, 'mem')])[0], hint=sparks.mem|safe) }}
     {%- set inodes_worse = inodes_root is defined and inodes_root is not none and (disk_root is none or inodes_root > disk_root) %}
     {{ stat_tile("Disk /", pct(disk_root) ~ (" · inodes " ~ pct(inodes_root) if inodes_worse else ""),
                  state=(grades.disk or [status_class(disk_root, 'disk')])[0], hint=sparks.disk|safe) }}
     {{ stat_tile("Load per core", pct(load_per_core), state=(grades.load or [status_class(load_per_core, 'load')])[0], hint=sparks.load|safe) }}
+    {% if temp is not none %}
+    {%- set temp_hint %}{{ sparks.temp|safe }}{% if hottest %}<span class="stat-tile-sensor" title="{{ hottest }}">{{ hottest }}</span>{% endif %}{% endset %}
+    {{ stat_tile("Temperature", deg(temp), state=status_class(temp, 'temp'), hint=temp_hint) }}
+    {% endif %}
   </div>
   {% if usual and not stale %}
   <p class="field-hint" style="margin-top:0.6rem;">{{ usual | join("; ") | capitalize }}.</p>