Layout Reader V27

[joseph-isaacs]

Summary

• merge current origin/develop into ji/layout27 and remove the duplicate layout_v2 implementation in favor of the layout vtable now on develop
• retain the heap-allocated V2 ScanPlan for expression pushdown and physical-plan binding
• register V1 layout splits before optimization, then bind projection and filter conjuncts once
• execute the bound plan through the established V1 LayoutReader split loop using expression-free pruning, filtering, and projection calls
• preserve V1 dynamic-filter version tracking, re-pruning, adaptive conjunct ordering, and filtered projection behavior
• keep V1 and V2 available side by side through VORTEX_SCAN_IMPL=v1|v2
• keep statistics and aggregate paths separate from normal scan execution

Correctness validation

• V1/V2 differential scan suite: 26/26 cases passed
• TPC-H SF1, Vortex format: 22/22 queries passed under VORTEX_SCAN_IMPL=v1
• TPC-H SF1, Vortex format: 22/22 queries passed under VORTEX_SCAN_IMPL=v2
• ClickBench partitioned dataset, all 100 shards: 43/43 queries passed under VORTEX_SCAN_IMPL=v1
• ClickBench partitioned dataset, all 100 shards: 43/43 queries passed under VORTEX_SCAN_IMPL=v2
• cargo test -p vortex-layout -p vortex-file --all-features --no-run
• cargo check -p vortex-layout -p vortex-file
• cargo check -p vortex-datafusion -p vortex-duckdb --all-features
• cargo clippy --all-targets --all-features
• cargo +nightly fmt --all
• git diff --check

Benchmark runs were evaluated for correctness only; their timings are not used as performance evidence in this PR.