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
