fix(cubesys): ls on directory paths no longer rejected by path_to_czyx

The ls handler used path_to_czyx() (which enforces "path must name a
record") to derive the ACL gate coordinate. Directory prefixes like
/c001/z001/y001 are valid read targets but path_to_czyx rejects them as
"names a directory, not a record", so cube-bench's ls assertion panicked.

Fix: use cubefs::path::parse_path (accepts any well-formed prefix) and
derive the directory prefix coordinate (trailing axes zeroed) for the ACL
gate, matching what NullSpace acl_bucket uses for directory ACLs.

Also: clippy -D warnings — remove unnecessary `c as u8` cast in
hash_backend_keys_sorted_order test.

Verification: cube-bench runs to completion (ls section printed OK),
clippy clean.

Co-Authored-By: Hermes Agent

cubestore/src/lib.rs

@@ -887,7 +887,7 @@ mod tests {
     fn hash_backend_keys_sorted_order() {
         let mut b = HashBackend::new();
         for c in 1u8..=3 {
-            b.put(Czyx::new(50, c, 10, 1), vec![c as u8]);
+            b.put(Czyx::new(50, c, 10, 1), vec![c]);
         }
         let keys = b.keys();
         assert_eq!(keys.len(), 3);