feat: support log.level JSON key for level detection (#4564)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/container/level_guesser.go

@@ -39,7 +39,7 @@ var singleLetterBracket = regexp.MustCompile(`\[([EWIDFTV])\]`)
 var timestampRegex = regexp.MustCompile(`^(?:\d{4}[-/]\d{2}[-/]\d{2}(?:[T ](?:\d{2}:\d{2}:\d{2}(?:\.\d+)?Z?|\d{2}:\d{2}(?:AM|PM)))?\s+)`)
 
 // JSON keys to check for log level (in priority order).
-var levelKeys = []string{"@l", "level", "severity"}
+var levelKeys = []string{"@l", "level", "log.level", "severity"}
 
 func init() {
 	SupportedLogLevels = make(map[string]struct{}, len(logLevels)+1)

internal/container/types.go

@@ -75,11 +75,16 @@ func FromProto(c *pb.Container) Container {
 		})
 	}
 
+	labels := c.Labels
+	if labels == nil {
+		labels = make(map[string]string)
+	}
+
 	return Container{
 		ID:          c.Id,
 		Name:        c.Name,
 		Image:       c.Image,
-		Labels:      c.Labels,
+		Labels:      labels,
 		Group:       c.Group,
 		Created:     c.Created.AsTime(),
 		State:       c.State,