fix: always strip slog time field — process manager provides timestamps

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

Author: ysyneu

cmd/main.go

@@ -244,10 +244,10 @@ func setupLogging(levelStr string) {
 	level := parseLogLevel(levelStr)
 	opts := &slog.HandlerOptions{
 		Level: level,
-		// Strip slog's time field when running under systemd/journald,
-		// which already prepends its own timestamp to every line.
+		// Strip slog's time field — the process manager (systemd/journald)
+		// already prepends its own timestamp to every line.
 		ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
-			if a.Key == slog.TimeKey && os.Getenv("INVOCATION_ID") != "" {
+			if a.Key == slog.TimeKey {
 				return slog.Attr{}
 			}
 			return a