feat(hosts): the hottest sensor is named with its chip, and the host-reading cutoffs are read and set over MCP (#6806)

Agent 1.27.0 sends each temperature sensor's hwmon chip. Steward keeps the
chip per host and label beside the reading, so a sensor's metric key stays
its label, and the strip and the heat alert name it as "NVMe · Sensor 2"
rather than a bare "Sensor 2".

get_thresholds (viewer) and set_thresholds (admin, audited) read and change
the warn/crit cutoffs CPU, memory, disk, load and temperature are graded by,
as Settings → Thresholds does.

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

plugins/host_agent/routes.py

@@ -124,13 +124,15 @@ def is_thermometer(host_name: str, label: str, celsius: float) -> bool:
 
 def hottest_sensor(host_name: str, temps: dict[str, float]) -> list[str]:
     """Which sensor sets a host's temperature, as an alert on it says:
-    ["Package id 0 at 86°C"], or [] with no thermometer among `temps`."""
+    ["CPU · Package id 0 at 86°C"], or [] with no thermometer among `temps`.
+    The chip leads the label when the host's agent has said which it is."""
     from steward.core.formatting import metric_value
     real = {label: c for label, c in temps.items() if is_thermometer(host_name, label, c)}
     if not real:
         return []
+    from .sensors import sensor_name
     label = max(real, key=real.get)
-    return [f"{label} at {metric_value('temp_c', real[label])}"]
+    return [f"{sensor_name(host_name, label)} at {metric_value('temp_c', real[label])}"]
 
 
 async def name_hottest_sensor(session, resource: str) -> list[str]:
@@ -374,6 +376,8 @@ def _expand_sample_to_metrics(
     # counts only readings that can be real (#5759), from sensors that behave
     # like thermometers (#5783).
     max_temp: float | None = None
+    from .sensors import note_chips
+    note_chips(host_name, sample.get("temps"))
     for t in sample.get("temps") or []:
         c = t.get("celsius")
         if c is None: