feat(nvidia_bug_report): extract Xid/SXid GPU error events

Parse Xid and SXid entries from the kernel log into GPU error events with
severity and the decoded failure reason.

See ADL-055.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

internal/parser/vendors/nvidia_bug_report/psu.go

@@ -32,6 +32,7 @@ func parsePSUInfo(content string, result *models.AnalysisResult) {
 			if currentPSU != nil && currentPSU.Slot != "" {
 				// Only add if PSU is present
 				if strings.Contains(strings.ToLower(currentPSU.Status), "present") {
+					currentPSU.Present = true
 					result.Hardware.PowerSupply = append(result.Hardware.PowerSupply, *currentPSU)
 				}
 			}
@@ -91,6 +92,7 @@ func parsePSUInfo(content string, result *models.AnalysisResult) {
 	// Save last PSU if exists
 	if currentPSU != nil && currentPSU.Slot != "" {
 		if strings.Contains(strings.ToLower(currentPSU.Status), "present") {
+			currentPSU.Present = true
 			result.Hardware.PowerSupply = append(result.Hardware.PowerSupply, *currentPSU)
 		}
 	}