Fix NVIDIA GPU serial number format extraction

Extract decimal serial numbers from devname parameters (e.g., "SXM5_SN_1653925027099")
instead of hex PCIe Device Serial Numbers. This provides the correct GPU serial
numbers as they appear in NVIDIA diagnostics tooling.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

internal/parser/vendors/nvidia/inventory_log_test.go

@@ -39,9 +39,10 @@ func TestParseInventoryLog(t *testing.T) {
 
 	content := string(inventoryLog.Content)
 
-	// Test devname regex
+	// Test devname regex - this extracts both slot mapping and serial numbers
 	t.Log("Testing devname extraction:")
 	lines := strings.Split(content, "\n")
+	serialCount := 0
 	for i, line := range lines {
 		if strings.Contains(line, "devname=") && strings.Contains(line, "fieldiag") {
 			t.Logf("Line %d: Found fieldiag command", i)
@@ -49,34 +50,29 @@ func TestParseInventoryLog(t *testing.T) {
 			t.Logf("  Found %d devname matches", len(matches))
 			for _, match := range matches {
 				if len(match) == 3 {
-					t.Logf("    PCI: %s -> Slot: %s", match[1], match[2])
+					pciBDF := match[1]
+					slotName := match[2]
+					t.Logf("    PCI: %s -> Slot: %s", pciBDF, slotName)
+
+					// Extract serial number from slot name
+					if strings.HasPrefix(slotName, "SXM") {
+						parts := strings.Split(slotName, "_")
+						if len(parts) == 3 && parts[1] == "SN" {
+							serial := parts[2]
+							t.Logf("      Serial: %s", serial)
+							serialCount++
+						}
+					}
 				}
 			}
 			break
 		}
 	}
+	t.Logf("\nTotal GPU serials extracted: %d", serialCount)
 
-	// Test lspci regex
-	t.Log("\nTesting lspci BDF extraction:")
-	serialCount := 0
-	bdfCount := 0
-	for i, line := range lines {
-		// Check for lines that look like lspci headers
-		if strings.Contains(line, "3D controller") && strings.Contains(line, "NVIDIA") {
-			t.Logf("Line %d: Potential lspci line: %q (starts with: %q)", i, line[:min(80, len(line))], line[:min(10, len(line))])
-			if match := pciBDFRegex.FindStringSubmatch(line); len(match) > 1 {
-				bdfCount++
-				t.Logf("  -> Matched BDF: %s", match[1])
-			} else {
-				t.Logf("  -> NO MATCH")
-			}
-		}
-		if match := gpuSerialRegex.FindStringSubmatch(line); len(match) > 1 {
-			serialCount++
-		}
+	if serialCount == 0 {
+		t.Error("Expected to find GPU serial numbers, but found none")
 	}
-	t.Logf("\nTotal BDFs found: %d", bdfCount)
-	t.Logf("Total serials found: %d", serialCount)
 }
 
 func min(a, b int) int {