fix: bump Lance for custom S3 endpoints

[dcfocus]

Summary

• bump Rust Lance crates to 9.0.0 and pylance to 9.x so MemWAL preserves storage/session parameters for derived WAL paths
• update Lance 9 scanner API call sites and make WAL-backed pagination deterministic with a narrow id sort before wide-row fetches
• make WAL-to-base cleanup idempotent under racing/interrupted merges by merge-inserting newest rows by key and skipping stale prepared commits
• remove the S3 custom-endpoint xfails and verify reopened Context handles can read moto-backed S3 writes
• handle Lance 9 internal MemWAL _tombstone column during WAL-to-base merges

Closes #197.

Upstream fix: lance-format/lance#7735, released in Lance v9.0.0.

Testing

• uv run --extra tests pytest -q
• uv run --extra dev ruff format --check .
• uv run --extra dev ruff check .
• uv run --extra dev pyright
• uv lock --check
• cargo-fmt --all -- --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo clippy -p lance-context-core --all-targets -- -D warnings
• cargo clippy -p lance-context-master --all-targets -- -D warnings
• cargo check -p lance-context-core
• cargo check -p lance-context-master
• cargo test -p lance-context-master --all-targets
• cargo test -p lance-context-core --all-targets
• cargo test -p lance-context-core rollout_store::tests::wal_and_all_pagination_take_only_page_rows
• cargo test -p lance-context-core rollout_store::tests::close_drains_resident_writer_and_add_reopens
• cargo test -p lance-context-core --test wal_merge_concurrency concurrent_merges_do_not_duplicate_rows