fix(metrics): parse rocm-smi CSV by header keywords, not column position

MI250X outputs 7 temperature columns before power/use%; positional parsing
read junction temp (~40°C) as GPU utilisation. Switch to header-based
colIdx() lookup so the correct fields are read regardless of column order
or rocm-smi version.

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

audit/internal/platform/gpu_metrics.go

@@ -78,48 +78,56 @@ func SampleGPUMetrics(gpuIndices []int) ([]GPUMetricRow, error) {
 
 // sampleAMDGPUMetrics queries rocm-smi for live GPU metrics.
 func sampleAMDGPUMetrics() ([]GPUMetricRow, error) {
-	// --showtemp --showuse --showpower --csv — one row per GPU
 	out, err := runROCmSMI("--showtemp", "--showuse", "--showpower", "--showmemuse", "--csv")
 	if err != nil {
 		return nil, err
 	}
-	var rows []GPUMetricRow
-	for _, line := range strings.Split(strings.TrimSpace(string(out)), "\n") {
-		line = strings.TrimSpace(line)
-		if line == "" || strings.HasPrefix(strings.ToLower(line), "device") {
-			continue
-		}
-		// CSV format: device,temp_c,gpu_use%,mem_use%,power_w (order may vary by rocm-smi version)
-		// We parse by column header from the first line.
-		parts := strings.Split(line, ",")
-		if len(parts) < 2 {
-			continue
-		}
-		idx := len(rows)
-		row := GPUMetricRow{GPUIndex: idx}
-		// rocm-smi CSV columns vary; extract what we can
-		for i, p := range parts {
-			p = strings.TrimSpace(p)
-			switch {
-			case i == 0:
-				// device index like "card0" or "0"
-			case strings.Contains(strings.ToLower(p), "n/a"):
-				// skip N/A
-			default:
-				// Try to match by position heuristic: temp, use%, memuse%, power
-				v := parseGPUFloat(p)
-				switch {
-				case i == 1 && row.TempC == 0:
-					row.TempC = v
-				case i == 2 && row.UsagePct == 0:
-					row.UsagePct = v
-				case i == 3 && row.MemUsagePct == 0:
-					row.MemUsagePct = v
-				case i == 4 && row.PowerW == 0:
-					row.PowerW = v
+	lines := strings.Split(strings.TrimSpace(string(out)), "\n")
+	if len(lines) < 2 {
+		return nil, fmt.Errorf("rocm-smi: insufficient output")
+	}
+
+	// Parse header to find column indices by name.
+	headers := strings.Split(lines[0], ",")
+	colIdx := func(keywords ...string) int {
+		for i, h := range headers {
+			hl := strings.ToLower(strings.TrimSpace(h))
+			for _, kw := range keywords {
+				if strings.Contains(hl, kw) {
+					return i
 				}
 			}
 		}
+		return -1
+	}
+	idxTemp := colIdx("sensor edge", "temperature (c)", "temp")
+	idxUse := colIdx("gpu use (%)")
+	idxMem := colIdx("vram%", "memory allocated")
+	idxPow := colIdx("average graphics package power", "power (w)")
+
+	var rows []GPUMetricRow
+	for _, line := range lines[1:] {
+		line = strings.TrimSpace(line)
+		if line == "" {
+			continue
+		}
+		parts := strings.Split(line, ",")
+		idx := len(rows)
+		row := GPUMetricRow{GPUIndex: idx}
+		get := func(i int) float64 {
+			if i < 0 || i >= len(parts) {
+				return 0
+			}
+			v := strings.TrimSpace(parts[i])
+			if strings.EqualFold(v, "n/a") {
+				return 0
+			}
+			return parseGPUFloat(v)
+		}
+		row.TempC = get(idxTemp)
+		row.UsagePct = get(idxUse)
+		row.MemUsagePct = get(idxMem)
+		row.PowerW = get(idxPow)
 		rows = append(rows, row)
 	}
 	if len(rows) == 0 {