Empties one cell. Out-of-range coordinates are ignored.

Creates a square grid. `cellSize` is the cell's width and height.

Creates a hex grid: hexagons of the spec's `Radius` (center to corner) stored as offset columns and rows. `CellSize` holds the hexagon's bounding box.

Reads one cell. Answers `ValueNone` for an empty cell and for out-of-range coordinates.

The world position of a cell. Square grids step by `CellSize`; hex grids stagger every other row (pointy top) or column (flat top).

The hex orientation of a hex-geometry grid. Throws for square grids.

The hex radius (center to corner) of a hex-geometry grid. Throws for square grids.

Calls `action` once per populated cell, in row-major order, with the cell's coordinates and content. Empty cells are skipped.

Iterates the cells that intersect a pixel rect, with orientation-aware culling for hex grids (every other row or column staggers, so the window is padded by one cell on each axis). The bounds are conservative: the window may include cells whose hexagon does not touch the rect, but never misses one that does.

Writes `content` into one cell. Out-of-range coordinates are ignored, so a section walk needs no bounds check.

The inclusive cell range a world-space pixel rect touches. Square grids map the rect through the origin and the cell size; hex grids stagger every other row or column, so the range is padded by one cell on each axis. The bounds are conservative: the range may include cells whose hexagon does not touch the rect, but never misses one that does. The tuple is `struct (startX, endX, startY, endY)`, ready for the two loops a window walk runs — `CellGrid2D.iterVisible` and `Occupancy.iterInWindow` both read it.