docs(logger): clarify ConfigureFromEnv godoc about log level config

The function only handles PICOCLAW_LOG_FILE for file logging.
PICOCLAW_LOG_LEVEL is handled separately in pkg/config/gateway.go.

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

pkg/logger/logger.go

@@ -217,6 +217,9 @@ func DisableFileLogging() {
 	}
 }
 
+// ConfigureFromEnv reads PICOCLAW_LOG_FILE from the environment and
+// enables file logging if set. The log level is controlled separately
+// via PICOCLAW_LOG_LEVEL in the config/gateway package.
 func ConfigureFromEnv() {
 	if logFile := os.Getenv("PICOCLAW_LOG_FILE"); logFile != "" {
 		if strings.HasPrefix(logFile, "~/") {