Fix GPU model propagation, export filenames, PSU/service status, and chart perf

- nvidia.go: add Name field to nvidiaGPUInfo, include model name in
  nvidia-smi query, set dev.Model in enrichPCIeWithNVIDIAData
- pages.go: fix duplicate GPU count in validate card summary (4 GPU: 4 x …
  → 4 x … GPU); fix PSU UNKNOWN fallback from hw.PowerSupplies; treat
  activating/deactivating/reloading service states as OK in Runtime Health
- support_bundle.go: use "150405" time format (no colons) for exFAT compat
- sat.go / benchmark.go / platform_stress.go / sat_fan_stress.go: remove
  .tar.gz archive creation from export dirs — export packs everything itself
- charts_svg.go: add min-max downsampling (1400 pt cap) for SVG chart perf
- benchmark_report.go / sat.go: normalize GPU fallback to "Unknown GPU"

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

audit/internal/webui/charts_svg.go

@@ -83,6 +83,10 @@ func renderMetricChartSVG(title string, labels []string, times []time.Time, data
 		}
 	}
 
+	// Downsample to at most ~1400 points (one per pixel) before building SVG.
+	times, datasets = downsampleTimeSeries(times, datasets, 1400)
+	pointCount = len(times)
+
 	statsLabel := chartStatsLabel(datasets)
 
 	legendItems := []metricChartSeries{}
@@ -196,6 +200,19 @@ func drawGPUOverviewChartSVG(title string, labels []string, times []time.Time, s
 		}
 	}
 
+	// Downsample to at most ~1400 points before building SVG.
+	{
+		datasets := make([][]float64, len(series))
+		for i := range series {
+			datasets[i] = series[i].Values
+		}
+		times, datasets = downsampleTimeSeries(times, datasets, 1400)
+		pointCount = len(times)
+		for i := range series {
+			series[i].Values = datasets[i]
+		}
+	}
+
 	scales := make([]chartScale, len(series))
 	for i := range series {
 		min, max := chartSeriesBounds(series[i].Values)
@@ -626,6 +643,87 @@ func writeTimelineBoundaries(b *strings.Builder, layout chartLayout, start, end
 	b.WriteString(`</g>` + "\n")
 }
 
+// downsampleTimeSeries reduces the time series to at most maxPts points using
+// min-max bucketing. Each bucket contributes the index of its min and max value
+// (using the first full-length dataset as the reference series). All parallel
+// datasets are sampled at those same indices so all series stay aligned.
+// If len(times) <= maxPts the inputs are returned unchanged.
+func downsampleTimeSeries(times []time.Time, datasets [][]float64, maxPts int) ([]time.Time, [][]float64) {
+	n := len(times)
+	if n <= maxPts || maxPts <= 0 {
+		return times, datasets
+	}
+	buckets := maxPts / 2
+	if buckets < 1 {
+		buckets = 1
+	}
+	// Use the first dataset that has the same length as times as the reference
+	// for deciding which two indices to keep per bucket.
+	var ref []float64
+	for _, ds := range datasets {
+		if len(ds) == n {
+			ref = ds
+			break
+		}
+	}
+	selected := make([]int, 0, maxPts)
+	bucketSize := float64(n) / float64(buckets)
+	for b := 0; b < buckets; b++ {
+		lo := int(math.Round(float64(b) * bucketSize))
+		hi := int(math.Round(float64(b+1) * bucketSize))
+		if hi > n {
+			hi = n
+		}
+		if lo >= hi {
+			continue
+		}
+		if ref == nil {
+			selected = append(selected, lo)
+			if hi-1 != lo {
+				selected = append(selected, hi-1)
+			}
+			continue
+		}
+		minIdx, maxIdx := lo, lo
+		for i := lo + 1; i < hi; i++ {
+			if ref[i] < ref[minIdx] {
+				minIdx = i
+			}
+			if ref[i] > ref[maxIdx] {
+				maxIdx = i
+			}
+		}
+		if minIdx <= maxIdx {
+			selected = append(selected, minIdx)
+			if maxIdx != minIdx {
+				selected = append(selected, maxIdx)
+			}
+		} else {
+			selected = append(selected, maxIdx)
+			if minIdx != maxIdx {
+				selected = append(selected, minIdx)
+			}
+		}
+	}
+	outTimes := make([]time.Time, len(selected))
+	for i, idx := range selected {
+		outTimes[i] = times[idx]
+	}
+	outDatasets := make([][]float64, len(datasets))
+	for d, ds := range datasets {
+		if len(ds) != n {
+			outDatasets[d] = ds
+			continue
+		}
+		out := make([]float64, len(selected))
+		for i, idx := range selected {
+			out[i] = ds[idx]
+		}
+		outDatasets[d] = out
+	}
+	return outTimes, outDatasets
+}
+
 func chartXForTime(ts, start, end time.Time, left, right int) float64 {
 	if !end.After(start) {
 		return float64(left+right) / 2