feat(audit): add platform thermal cycling stress test

Runs CPU (stressapptest) + GPU stress simultaneously across multiple
load/idle cycles with varying idle durations (120s/60s/30s) to detect
cooling systems that fail to recover under repeated load.

Presets: smoke (~5 min), acceptance (~25 min), overnight (~100 min).
Outputs metrics.csv + summary.txt with per-cycle throttle and fan
spindown analysis, packed as tar.gz.

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

audit/internal/app/app.go

@@ -120,6 +120,7 @@ type satRunner interface {
 	RunMemoryStressPack(ctx context.Context, baseDir string, durationSec int, logFunc func(string)) (string, error)
 	RunSATStressPack(ctx context.Context, baseDir string, durationSec int, logFunc func(string)) (string, error)
 	RunFanStressTest(ctx context.Context, baseDir string, opts platform.FanStressOptions) (string, error)
+	RunPlatformStress(ctx context.Context, baseDir string, opts platform.PlatformStressOptions, logFunc func(string)) (string, error)
 	RunNCCLTests(ctx context.Context, baseDir string, logFunc func(string)) (string, error)
 }
 
@@ -627,6 +628,13 @@ func (a *App) RunFanStressTest(ctx context.Context, baseDir string, opts platfor
 	return a.sat.RunFanStressTest(ctx, baseDir, opts)
 }
 
+func (a *App) RunPlatformStress(ctx context.Context, baseDir string, opts platform.PlatformStressOptions, logFunc func(string)) (string, error) {
+	if strings.TrimSpace(baseDir) == "" {
+		baseDir = DefaultSATBaseDir
+	}
+	return a.sat.RunPlatformStress(ctx, baseDir, opts, logFunc)
+}
+
 func (a *App) RunNCCLTestsResult(ctx context.Context) (ActionResult, error) {
 	path, err := a.sat.RunNCCLTests(ctx, DefaultSATBaseDir, nil)
 	body := "Results: " + path

audit/internal/app/app_test.go

@@ -203,6 +203,10 @@ func (f fakeSAT) RunFanStressTest(_ context.Context, _ string, _ platform.FanStr
 	return "", nil
 }
 
+func (f fakeSAT) RunPlatformStress(_ context.Context, _ string, _ platform.PlatformStressOptions, _ func(string)) (string, error) {
+	return "", nil
+}
+
 func (f fakeSAT) RunNCCLTests(_ context.Context, _ string, _ func(string)) (string, error) {
 	return "", nil
 }