fix: error-pages graded healthy, unwired sensors listed apart, Maintenance failed reads 0 (#5780, #5781, #5782)

- #5780 "The error-pages service is graded on other routers' errors". The
  Traefik scrape reads which services an errors middleware sends to, and
  grades them healthy: their 4xx and 5xx are the codes of the errors they
  cover for, already graded on the routers that failed.
- #5781 "The Maintenance failed rules sit at no data until a host has had
  a maintenance job". Every host with an agent reads 0 until a job fails.
- #5782 "VDNT-Util01's host page lists SYSTIN at 115 °C in red". The host
  page lists sensors that counts_as_hottest leaves out (unwired board
  inputs, 0 °C or below) on one muted line, not as heat.

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

tests/integration/test_host_maintenance_cadence.py

@@ -107,7 +107,9 @@ def test_hosts_go_one_at_a_time_and_a_failure_stops_the_run():
             async with s.begin():
                 plan = await s.get(models.HostMaintenancePlan, seed["plan_id"])
                 await cadence.start_run(s, plan, datetime.now(timezone.utc), manual=True)
-        await _tick(app)
+        first = await _tick(app)
+        # Before any job finishes, every agent host reads 0 rather than nothing.
+        assert first[seed["hosts"]["a"].name] == 0.0 and first[seed["hosts"]["b"].name] == 0.0
 
         # Only the first host (by name) has a job; the second waits.
         ta, tb = seed["tokens"]["a"], seed["tokens"]["b"]

tests/plugins/host_agent/test_expand_metrics.py

@@ -156,3 +156,13 @@ def test_the_registration_keeps_the_host_s_updates_and_reboot():
                         "reboot": {"required": False}}, now)
     assert reg.updates_pending == 4 and reg.updates_error == "apt is locked"
     assert reg.reboot_required is False and reg.reboot_required_since is None
+
+
+def test_the_page_lists_unwired_sensors_apart_hottest_first():
+    """VDNT-Util01's sensor list read SYSTIN 115 °C in red at the top, though
+    the host's temperature already left it out (#5759)."""
+    from plugins.host_agent.routes import split_temps
+    real, unwired = split_temps({"SYSTIN": 115.0, "AUXTIN0": 110.0, "Package id 0": 52.0,
+                                 "Composite": 48.9, "PCH_CHIP_TEMP": 0.0, "CPUTIN": 47.0, "gone": None})
+    assert list(real) == ["Package id 0", "Composite", "CPUTIN", "gone"]
+    assert list(unwired) == ["SYSTIN", "AUXTIN0", "PCH_CHIP_TEMP"]

tests/plugins/traefik/test_meaning.py

@@ -127,3 +127,24 @@ async def test_a_card_for_an_unknown_service_says_so(app):
     assert "Status codes not recorded yet" in card
     assert "The app is answering with server errors" in card
     assert "Steward can't tell which service serves this router" in card
+
+
+def test_the_error_pages_service_is_found_from_traefiks_errors_middlewares():
+    from plugins.traefik.scraper import error_page_services
+    got = error_page_services([
+        {"name": "error-pages@swarm", "provider": "swarm", "errors": {"service": "error-pages-service",
+                                                                      "status": ["400-599"]}},
+        {"name": "other@file", "errors": {"service": "pages@docker"}},      # already names its provider
+        {"name": "https-redirect@swarm", "redirectScheme": {"scheme": "https"}},
+    ])
+    assert got == {"error-pages-service@swarm", "pages@docker"}
+
+
+def test_the_error_pages_service_is_healthy_whatever_its_codes():
+    """It answers with the code of the error it covers for (#5780)."""
+    from plugins.traefik.routes import ERROR_PAGES_WHY, grade_routers
+    routers = [{"name": "error-pages-service@swarm", "latest": _latest(e4=90.0, e5=8.0)},
+               {"name": "app@swarm", "latest": _latest(e5=8.0)}]
+    grade_routers(routers, {}, TH, error_pages=frozenset({"error-pages-service@swarm"}))
+    assert (routers[0]["state"], routers[0]["why"], routers[0]["kind"]) == ("ok", ERROR_PAGES_WHY, None)
+    assert routers[1]["state"] == "crit" and routers[1]["kind"] == "5xx"