fix: Implement fallback log directory for file logging on read-only systems.

internal/logging/global_logger.go

@@ -95,6 +95,13 @@ func ConfigureLogOutput(loggingToFile bool, logsMaxTotalSizeMB int) error {
 	logDir := "logs"
 	if base := util.WritablePath(); base != "" {
 		logDir = filepath.Join(base, "logs")
+	} else if loggingToFile {
+		// When logging to file is enabled but WRITABLE_PATH is not set,
+		// use a default writable location to avoid errors on read-only filesystems
+		// (e.g., Homebrew installations on macOS).
+		if home, err := os.UserHomeDir(); err == nil {
+			logDir = filepath.Join(home, ".cliproxyapi", "logs")
+		}
 	}
 
 	protectedPath := ""