Forward local_file through DirFileSystem - #2212

Fixes #1110.

DirFileSystem wraps a filesystem but does not expose its local_file flag. A directory wrapper around LocalFileSystem therefore fails the local-file check in open_local even though its files are local.

Add a property alongside the existing sep property that reads the wrapped filesystem's local_file flag, defaulting to False when the wrapped filesystem has no flag. This follows the passthrough approach efiop suggested in the issue and martindurant invited a contribution for.

Tests cover local and memory filesystems, nested directory wrappers, an explicit False flag, and open_local's accept/reject checks. The local test opens a real file through OpenFile/OpenFiles. Only URL-to-filesystem construction is substituted so open_local receives the already constructed wrapper.

Verification

• Baseline: 5 new cases fail with missing local_file.
• Patched: directory/cache/core/spec suites 622 passed, 48 skipped, 1 xfailed on Linux/Python 3.10.12.
• Independent fresh-clone runner: baseline 5 failures, directory/core/spec suite 517 passed, 17 skipped, 1 xfailed.
• Ruff 0.14.3 check/format and git diff --check clean.
• Dev/Fixes changelog entry included.