chore: remove unused dependencies and dead code

Co-authored-by: aider (openai/andrew.openrouter.qwen.qwen3-coder) <aider@aider.chat>

src/compression_engine/program.rs

@@ -94,21 +94,3 @@ impl CompressionEngine for CompressionEngineProgram {
         Ok(Box::new(process.stdin.unwrap()))
     }
 }
-
-fn get_program_path(program: &str) -> Result<String> {
-    debug!("COMPRESSION: Looking for executable: {}", program);
-    if let Ok(path) = env::var("PATH") {
-        for p in path.split(':') {
-            let p_str = format!("{}/{}", p, program);
-            let stat = fs::metadata(p_str.clone());
-            if let Ok(stat) = stat {
-                let md = stat;
-                let permissions = md.permissions();
-                if md.is_file() && permissions.mode() & 0o111 != 0 {
-                    return Ok(p_str);
-                }
-            }
-        }
-    }
-    Err(anyhow!("Unable to find binary {} in PATH", program))
-}