fix: enforce deletion vector scan applicability

[wirybeaver]

Summary

• require deletion vectors to match the data file partition spec ID and partition tuple
• compare partition tuples with typed StructLikeEqual, including null values
• treat older same-path deletion vectors as inapplicable and fall back to position deletes
• confirm applicable deletion vectors supersede file-scoped position deletes

Stacked on #913. Until #913 merges, this PR contains both commits; review commit dc84d6e for this change.

Related to #637.

Testing

• pre-commit hooks: passed
• GCC 14 DeleteFileIndexVersions/DeleteFileIndexTest.*: 50 passed, 8 expected skips

[wirybeaver]

Superseded by #919 as part of #916. Minimal partition/spec consistency checks are included with the end-to-end write/read feature, while existing fail-fast sequence semantics are preserved. The standalone prerequisite has been removed.