feat(vortex-geo): add intersection scalar function - #9220

Stacked on #9219.

Summary

• add native polygonal intersection overloads backed by geo::BooleanOps: Polygon × Polygon, Polygon × MultiPolygon, MultiPolygon × Polygon, and MultiPolygon × MultiPolygon
• return a native 2D MultiPolygon for every overload
• preserve constant/column execution and strict null propagation through the existing binary dispatcher
• add Q9-oriented coverage for overlap, disjoint, boundary-touching, holes, constants, nulls, and all four input-type combinations
• add focused rectangle and detailed-boundary microbenchmarks

NaN/invalid-coordinate checking remains outside the default execution path, consistent with the rest of the native geo scalar stack.

Checks

• cargo +nightly fmt --all
• cargo test -p vortex-geo (254 passed)
• cargo clippy -p vortex-geo --all-targets --all-features -- -D warnings
• cargo clippy --all-targets --all-features -- -D warnings
• cargo bench -p vortex-geo --bench intersection
• git diff --check