fix(io): adapt to zip 9 API

- last_modified_time takes DateTime directly, drop the Some() wrapper
- file_names() returns Result<Cow<str>, ZipError>: propagate errors, compare
  the Cow<str>, and push the resolved name into seen
- test helper: ZipFile::name() now returns Result, unwrap it
- update the Cargo.toml comment explaining why we moved ahead of
  SolidCraft (still on zip 3)
- update Cargo.lock to zip 9.0.3

crates/io/tests/file.rs

@@ -52,7 +52,7 @@ fn parts(bytes: &[u8]) -> Vec<(String, Vec<u8>)> {
             let mut f = zip.by_index(i).unwrap();
             let mut b = Vec::new();
             f.read_to_end(&mut b).unwrap();
-            (f.name().to_string(), b)
+            (f.name().unwrap().to_string(), b)
         })
         .collect()
 }