feat(sat): fan ceiling check + topology fan tiles

Repurpose the previously-unwired RunFanStressTest into RunFanCheck, a
Load-tier SAT test that drives stressapptest (CPU+memory) and, when a GPU
is present, a GPU burn to 100% simultaneously, then watches every fan
until none has climbed for ~60s. The observed peak RPM per fan is the
"ceiling"; it is persisted through the existing fan-observation store.

MSI G4201 / AMI MegaRAC exposes no host-side fan force (every OEM IPMI
command returns 0xc1; Redfish Thermal is GET-only), so load-driven ramp
is the closest safe equivalent. See
bible-local/decisions/2026-09-04-fan-ceiling-check.md.

- platform.ResolveFanMaxRPM: per-fan max with fallback (persisted peak ->
  peer peak -> current RPM), resolved in platform, not the view.
- platform.ErrTestNotApplicable: no load source or no fan sensors ->
  task lands as cancelled ("not applicable"), never failed, so an
  engineer never sees a false red. executeTaskWithOptions maps the
  sentinel; finalizeTaskForResult honours a pre-set TaskCancelled.
- Verdict FAIL only for a fan at 0 RPM / IPMI cr-nr under load.
- /topo: one small spinning square per fan, sized by RPM / resolved max,
  clickable through to a new "fan" component-detail type; per-fan status
  recorded to the component-status DB from the fan SAT summary.
- Wiring: /api/sat/fan/run route, "fan" task target, Load-page card,
  stress-mode Run All.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019VHG21rgTUiR1G3qFHTVmN

audit/internal/platform/sat_fan_stress_test.go

@@ -1,11 +1,68 @@
 package platform
 
 import (
+	"os"
 	"path/filepath"
+	"reflect"
 	"testing"
 	"time"
 )
 
+func TestResolveFanMaxRPM(t *testing.T) {
+	oldPath := fanObservationStatePath
+	oldInit := fanObservationInit
+	fanObservationStatePath = filepath.Join(t.TempDir(), "fan-observation.json")
+	fanObservationInit = false
+	t.Cleanup(func() {
+		fanObservationStatePath = oldPath
+		fanObservationInit = oldInit
+	})
+
+	// No persisted file yet: unknown fans fall back to their own current RPM.
+	got := ResolveFanMaxRPM(map[string]float64{"A": 4000, "B": 9000})
+	if !reflect.DeepEqual(got, map[string]float64{"A": 4000, "B": 9000}) {
+		t.Fatalf("no-persist fallback: got %v", got)
+	}
+
+	if err := os.WriteFile(fanObservationStatePath, []byte(`{"max_rpm":{"A":17000}}`), 0644); err != nil {
+		t.Fatal(err)
+	}
+	got = ResolveFanMaxRPM(map[string]float64{"A": 4000, "B": 9000, "C": 5000})
+	// A: persisted peak. B/C: no own entry -> largest peer peak (A's 17000).
+	if want := map[string]float64{"A": 17000, "B": 17000, "C": 17000}; !reflect.DeepEqual(got, want) {
+		t.Fatalf("peer fallback: got %v want %v", got, want)
+	}
+}
+
+func TestApplyFanCheckDefaults(t *testing.T) {
+	var o FanCheckOptions
+	applyFanCheckDefaults(&o)
+	if o.PlateauHoldSec != 60 || o.PlateauDeltaRPM != 50 || o.MinLoadSec != 90 || o.MaxLoadSec != 900 || o.RampConfirmRPM != 150 {
+		t.Fatalf("unexpected defaults: %+v", o)
+	}
+	o = FanCheckOptions{PlateauHoldSec: 120, MinLoadSec: 30, MaxLoadSec: 40}
+	applyFanCheckDefaults(&o)
+	if o.MinLoadSec < o.PlateauHoldSec {
+		t.Fatalf("MinLoadSec must be >= PlateauHoldSec, got %d", o.MinLoadSec)
+	}
+	if o.MaxLoadSec <= o.MinLoadSec {
+		t.Fatalf("MaxLoadSec must exceed MinLoadSec, got %d", o.MaxLoadSec)
+	}
+}
+
+func TestSanitizeSummaryKey(t *testing.T) {
+	for in, want := range map[string]string{
+		"F2U-1":          "F2U-1",
+		"aspeed / fan1":  "aspeed___fan1",
+		"CPU0_DIMM":      "CPU0_DIMM",
+		"weird=key here": "weird_key_here",
+	} {
+		if got := sanitizeSummaryKey(in); got != want {
+			t.Errorf("sanitizeSummaryKey(%q)=%q want %q", in, got, want)
+		}
+	}
+}
+
 func TestParseFanSpeeds(t *testing.T) {
 	raw := "FAN1 | 2400.000 | RPM | ok\nFAN2 | 1800 RPM | ok | ok\nFAN3 | na | RPM | ns\n"
 	got := parseFanSpeeds(raw)