Implement Filter Encoding v2 parity

[rustyconover]

Summary

• replace the legacy filter tree decoder with the current vgi.filters.v2 Arrow snapshot/delta consumer
• bind column, field, typed payload, and external-IN references authoritatively and evaluate the DuckDB standard-v1 predicate surface
• preserve dynamic filter state across validated revisioned deltas and expose truthful Filter-v2 capabilities
• implement SQL/Kleene NULL semantics, DuckDB NaN/signed-zero equality and ordering, checked arithmetic, constrained casts, and exact nested list_contains
• add the canonical split dynamic-filter fixture and focused evaluator/capability tests

Testing

• macOS build and ctest --test-dir build --output-on-failure (18/18)
• source-of-truth Filter-v2 worker corpus (29/29)
• EC2 GCC 14.2.1 build and CTest (18/18)
• EC2 canonical splits/dynamic_filters.test (18/18 assertions)
• EC2 GCC 14.2.1 full canonical suite on PR Implement Filter Encoding v2 parity #4 alone (343 total: 328 passed, 15 non-filter fixture gaps, 39 skipped; no Filter-v2 failures)
• combined PR Implement Filter Encoding v2 parity #4 + PR Add non-filter VGI integration parity fixtures #5 GCC 14.2.1 validation (23/23 unit, 343/343 canonical, bearer 7/7)

Depends conceptually on / supersedes the draft capability-only PR #3; its commit is included here.