feat(audit): fan-stress SAT for MSI case-04 fan lag & thermal throttle detection

Two-phase GPU thermal cycling test with per-second telemetry:
- Phases: baseline → load1 → pause (no cooldown) → load2 → cooldown
- Monitors: fan RPM (ipmitool sdr), CPU/server temps (ipmitool/sensors),
  system power (ipmitool dcmi), GPU temp/power/usage/clock/throttle (nvidia-smi)
- Detects throttling via clocks_throttle_reasons.active bitmask
- Measures fan response lag from load start (validates case-04 ~2s lag)
- Exports metrics.csv (wide format, one row/sec) and fan-sensors.csv (long format)
- TUI: adds [F] Fan Stress Test to Health Check screen with Quick/Standard/Express modes

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

audit/internal/tui/screen_health_check.go

@@ -18,16 +18,17 @@ const (
 
 // Cursor positions in Health Check screen.
 const (
-	hcCurGPU       = 0
-	hcCurMemory    = 1
-	hcCurStorage   = 2
-	hcCurCPU       = 3
-	hcCurSelectAll = 4
-	hcCurModeQuick = 5
-	hcCurModeStd   = 6
-	hcCurModeExpr  = 7
-	hcCurRunAll    = 8
-	hcCurTotal     = 9
+	hcCurGPU        = 0
+	hcCurMemory     = 1
+	hcCurStorage    = 2
+	hcCurCPU        = 3
+	hcCurSelectAll  = 4
+	hcCurModeQuick  = 5
+	hcCurModeStd    = 6
+	hcCurModeExpr   = 7
+	hcCurRunAll     = 8
+	hcCurFanStress  = 9
+	hcCurTotal      = 10
 )
 
 // hcModeDurations maps mode index (0=Quick,1=Standard,2=Express) to GPU stress seconds.
@@ -82,6 +83,8 @@ func (m model) updateHealthCheck(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 			m.hcMode = m.hcCursor - hcCurModeQuick
 		case hcCurRunAll:
 			return m.hcRunAll()
+		case hcCurFanStress:
+			return m.hcRunFanStress()
 		}
 	case "g", "G":
 		return m.hcRunSingle(hcGPU)
@@ -93,6 +96,8 @@ func (m model) updateHealthCheck(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 		return m.hcRunSingle(hcCPU)
 	case "r", "R":
 		return m.hcRunAll()
+	case "f", "F":
+		return m.hcRunFanStress()
 	case "a", "A":
 		allOn := m.hcSel[0] && m.hcSel[1] && m.hcSel[2] && m.hcSel[3]
 		for i := range m.hcSel {
@@ -143,6 +148,13 @@ func (m model) hcRunSingle(idx int) (tea.Model, tea.Cmd) {
 	return m, nil
 }
 
+func (m model) hcRunFanStress() (tea.Model, tea.Cmd) {
+	m.pendingAction = actionRunFanStress
+	m.screen = screenConfirm
+	m.cursor = 0
+	return m, nil
+}
+
 func (m model) hcRunAll() (tea.Model, tea.Cmd) {
 	for _, sel := range m.hcSel {
 		if sel {
@@ -300,8 +312,16 @@ func renderHealthCheck(m model) string {
 		fmt.Fprintf(&b, "%s[ RUN ALL [R] ]\n", pfx)
 	}
 
+	{
+		pfx := "  "
+		if m.hcCursor == hcCurFanStress {
+			pfx = "> "
+		}
+		fmt.Fprintf(&b, "%s[ FAN STRESS TEST [F] ]   (thermal cycling, fan lag, throttle check)\n", pfx)
+	}
+
 	fmt.Fprintln(&b)
 	fmt.Fprintln(&b, "─────────────────────────────────────────────────────────────────")
-	fmt.Fprint(&b, "[↑↓] move  [space/enter] toggle  [letter] single test  [R] run all  [Esc] back")
+	fmt.Fprint(&b, "[↑↓] move  [space/enter] toggle  [letter] single test  [R] run all  [F] fan stress  [Esc] back")
 	return b.String()
 }