data.copy / move / sync / verify -- high-level workflow API

[djdarcy]

Summary

Add a new dazzle_filekit.data submodule that exposes high-level file
operations (copy, move, sync, verify) which compose existing
filekit primitives with unctools and preservelib when available.

This is the primary user-facing entry point for the v0.3.0 "seamless
file operations" vision. See the epic for context.

API sketch

from dazzle_filekit import data

# Single-file copy with rich preservation
data.copy(
    src: Union[str, Path],
    dst: Union[str, Path],
    *,
    preserve: Literal["none", "basic", "all"] = "basic",
    verify: Optional[str] = None,           # None | "md5" | "sha256" | ...
    manifest: bool = False,
    overwrite: bool = False,
    dry_run: bool = False,
) -> CopyResult

data.move(src, dst, *, preserve="basic", verify=None, manifest=False, ...)
data.sync(src_dir, dst_dir, *, mode="mirror", verify=None, ...)
data.verify(path, expected_hash=None, *, algorithm="sha256") -> VerifyResult

CopyResult / VerifyResult are dataclasses with .success, .src,
.dst, .bytes_copied, .hash, .metadata, .warnings fields.

Behavior

• Input path handling: both src and dst go through the new
  parse_user_input_path() (sub-issue N+4) so the caller can pass
  any pasted form
• UNC translation: if unctools is installed AND the src/dst is a
  UNC path AND a local drive mapping exists, optionally translate
  (gated by a prefer_local_over_unc=True default)
• Preservation levels:
  • "none" -- content only, no metadata
  • "basic" -- existing copy_file(preserve_attrs=True) behavior
  • "all" -- full rich metadata via the v0.2.4 metadata module
    (SDDL ACLs, ctime, xattrs, ADS warnings)
• Verification: if verify="sha256", compute the hash before and
  after the copy, raise on mismatch
• Manifest: if manifest=True, use preservelib's manifest writer
  (or fall back to filekit's atomic_write_json with a minimal
  manifest schema if preservelib isn't installed)
• Dry run: dry_run=True returns a CopyResult with .success=False
  and a description of what would have happened, without touching disk

Acceptance criteria

• from dazzle_filekit import data works
• data.copy, data.move, data.sync, data.verify are callable
• data.copy(src, dst, preserve="all", verify="sha256", manifest=True)
  works end-to-end on both Windows and Linux
• Degrades gracefully when unctools / preservelib are missing
  (with clear error messages or documented fallbacks)
• Cross-platform test coverage via scripts/run-cross-platform-tests.sh
• Documentation includes a "seamless copy" example in the README

Dependencies

• Blocked by: #N+4 (parse_user_input_path), #N+3 (optional-peer
  integration pattern)
• Blocks: #N+7 (documentation), #N+2 (DataRef builds on these
  function entry points)

Non-goals

• This issue does NOT define the DataRef / object-style API -- that's
  sub-issue #N+2
• This issue does NOT tackle cross-runtime operation continuity (WSL
  alias detection) -- that's sub-issue #N+5