Use Linux openat2 with RESOLVE_BENEATH and RESOLVE_NO_SYMLINKS for LocalDisk I/O path validation while keeping the existing lstat walk as the public-path and unsupported-kernel fallback. Add focused regression coverage for traversal, symlink swaps, missing leaves, recreated parents, high-cardinality prefixes, final symlink leaves, and concurrent validation.
Co-authored-by: heihutu <[email protected]>