Address code review comments - add documentation and improve error handling

Co-authored-by: Byron <63622+Byron@users.noreply.github.com>

Author: Copilot

gix-archive/src/write.rs

@@ -185,7 +185,7 @@ fn append_zip_entry<W: std::io::Write + std::io::Seek>(
 
             let (mut zip_entry, config) = file_builder.start().map_err(std::io::Error::other)?;
 
-            // Use flate2 for compression
+            // Use flate2 for compression. Level 9 is the maximum compression level for deflate.
             let encoder = flate2::write::DeflateEncoder::new(
                 &mut zip_entry,
                 match compression_level {

gix-archive/tests/archive.rs

@@ -174,11 +174,11 @@ mod from_tree {
                 let ar = rawzip::ZipArchive::from_slice(buf.as_slice())?;
                 assert_eq!(
                     {
-                        let mut n: Vec<_> = ar.entries().filter_map(|e| {
-                            e.ok().map(|entry| {
-                                String::from_utf8_lossy(entry.file_path().as_ref()).to_string()
-                            })
-                        }).collect();
+                        let mut n: Vec<_> = Vec::new();
+                        for entry_result in ar.entries() {
+                            let entry = entry_result?;
+                            n.push(String::from_utf8_lossy(entry.file_path().as_ref()).to_string());
+                        }
                         n.sort();
                         n
                     },