[feat](csv) Distribute CSV reads and writes

[kaka11chen]

Summary

• Enable Ray CSV sources to distribute both multiple files and one seekable, uncompressed UTF-8 file as aligned byte-range scan tasks, with exact row ownership across quoted multiline fields, CR/LF/CRLF boundaries, BOMs, and UTF-8 code points.
• Serialize and rebuild CSV read/write bind state, union-by-name metadata, scan identities, casts, and COPY writer statistics so Ray workers execute CSV scans and writes without coordinator-only state.
• Preserve stable source-task identities for fault-tolerant execution and emit one distributed CSV output file per scan task.
• Reject unsupported distributed CSV configurations explicitly (compression, non-UTF-8 encodings, parallel = false, skip_rows, and store_rejects); this change intentionally adds no compatibility path or local fallback.

Related issue

N/A

Documentation impact

• No user-facing documentation update is required.
• Documentation is updated in this PR or in a linked website PR.
• A follow-up issue is required in
  AstroVela/vane-website.

The change extends the existing Ray runner implementation without adding a new public API. Its strict unsupported-option behavior is covered by tests and documented above.

Validation

• Incremental native install in Release mode with VANE_NATIVE_BUILD_JOBS=8 and SKBUILD_BUILD_DIR=$PWD/build/python-release.
• scripts/format workspace --from-ref upstream/main --check
• git diff --check upstream/main
• Regenerated serialize_nodes.cpp into a temporary directory and verified an exact diff against the checked-in generated source.
• scripts/run_installed_pytest.sh tests/fast/test_ray_relation_to_distributed_plan.py -q: 12 passed.
• scripts/run_installed_pytest.sh tests/fast/test_ray_e2e_serialization.py -q: 10 passed.
• scripts/run_installed_pytest.sh tests/fast/test_ray_result_contract.py -q: 224 passed.
• scripts/run_native_tests.sh "test/sql/copy/return_stats.test" -s: 332 assertions in 1 test case passed.
• scripts/run_release_tests.sh: passed; Ray shard 14 passed, 525 deselected.
• Randomized byte-range stress coverage: 12 seeds × 8 tasks over LF/CRLF/CR files, quoted delimiters/quotes, embedded newlines, Unicode, and missing final newlines.
• scripts/run_fast_tests.sh: non-Ray shard passed (5,972 passed, 622 skipped, 132 deselected, 7 xfailed, 1 xpassed); all new CSV Ray tests passed. The shared-Ray shard retained 15 unrelated generic Ray failures, and representative failures reproduced unchanged in a pristine upstream/main worktree on the same host.

Checklist

• The change is focused and includes tests or a reason tests are unnecessary.
• Public behavior and compatibility impact are documented.
• New dependencies, copied code, model assets, and datasets have compatible
  licenses and are recorded where required.
• No credentials, private endpoints, personal paths, generated data, model
  weights, or build artifacts are included.
• Security implications of UDFs, serialization, remote code, network access,
  and untrusted input have been considered.
• Native changes were compiled; Python-only, documentation, and workflow
  changes passed relevant checks.

No new dependencies, copied code, model assets, or datasets are introduced.