fix: resolve compilation errors and warnings in keep crate

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

src/compression_engine/program.rs

@@ -36,6 +36,24 @@ impl CompressionEngineProgram {
     }
 }
 
+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))
+}
+
 impl CompressionEngine for CompressionEngineProgram {
     fn is_supported(&self) -> bool {
         self.supported