Function grid_placements 

pub fn grid_placements(table: &Table) -> GridPlacements

Places every cell on the logical grid without validating the result.

This mirrors the historical HWPX encoder scan exactly — per-row cursor, skip positions occupied by earlier spans, mark this cell’s span occupied — including its silent tolerance of overlaps and ragged rows. Encoders and analysis passes use this to stay byte/behaviour-identical for existing documents; addressing surfaces must use TableGrid::from_table instead.