fix: add missing imports for sha2, Command, and Stdio

src/compression_engine/program.rs

@@ -5,6 +5,7 @@ use std::fs;
 use std::fs::File;
 use std::io::{Read, Write};
 use std::os::unix::fs::PermissionsExt;
+use std::process::{Command, Stdio};
 use std::path::PathBuf;
 
 use crate::compression_engine::CompressionEngine;