Adds `FilterMask` and conditional bitwise methods (`*_where`) to `obicompactvec` for composable column-based slot filtering. Extends `obikpartitionner` with a `MatrixGroupOps` trait and `column_mask_expr` method to express aggregate constraints as vectorized masks. Refactors matrix builder management into a unified `Builders` enum and introduces `try_compute_combined_mask`, enabling O(1) slot checks and skipping unnecessary row reads during partitioning and rebuilding passes.
Eric Coissac
7c1efa9cbb